181,777 research outputs found
A PCA-based bio-motion generator to synthesize new patterns of human running
[EN] Synthesizing human movement is useful for most applications where the use of avatars is required. These movements should be as realistic as possible and thus must take into account anthropometric characteristics (weight, height, etc.), gender, and the performance of the activity being developed. The aim of this study is to develop a new methodology based on the combination of principal component analysis and partial least squares regression model that can generate realistic motion from a set of data (gender, anthropometry and performance). A total of 18 volunteer runners have participated in the study. The joint angles of the main body joints were recorded in an experimental study using 3D motion tracking technology. A five-step methodology has been employed to develop a model capable of generating a realistic running motion. The described model has been validated for running motion, showing a highly realistic motion which fits properly with the real movements measured. The described methodology could be applied to synthesize any type of motion: walking, going up and down stairs, etc. In future work, we want to integrate the motion in realistic body shapes, generated with a similar methodology and from the same simple original data.The research for this paper was done within the EASY-IMP project (http://www.easy-imp.eu/) funded by the European Commission FP7.FoF.NMP.2013-5 Project 609078. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Baydal Bertomeu, JM.; Dura Gil, J.; Piérola Orcero, A.; Parrilla Bernabé, E.; Ballester Fernández, A.; Alemany Munt, S. (2016). A PCA-based bio-motion generator to synthesize new patterns of human running. PeerJ Computer Science. 4:1-16. https://doi.org/10.7717/peerj-cs.102S116
Non equilibrium effects in fragmentation
We study, using molecular dynamics techniques, how boundary conditions affect
the process of fragmentation of finite, highly excited, Lennard-Jones systems.
We analyze the behavior of the caloric curves (CC), the associated thermal
response functions (TRF) and cluster mass distributions for constrained and
unconstrained hot drops. It is shown that the resulting CC's for the
constrained case differ from the one in the unconstrained case, mainly in the
presence of a ``vapor branch''. This branch is absent in the free expanding
case even at high energies . This effect is traced to the role played by the
collective expansion motion. On the other hand, we found that the recently
proposed characteristic features of a first order phase transition taking place
in a finite isolated system, i.e. abnormally large kinetic energy fluctuations
and a negative branch in the TRF, are present for the constrained (dilute) as
well the unconstrained case. The microscopic origin of this behavior is also
analyzed.Comment: 21 pages, 11 figure
Distinction of disorder, classical and quantum vibrational contributions to atomic mean-square amplitudes in dielectric pentachloronitrobenzene
The solid-state molecular disorder of pentachloronitrobenzene (PCNB) and its
role in causing anomalous dielectric properties are investigated. Normal
coordinate analysis (NCA) of atomic mean-square displacement parameters (ADPs)
is employed to distinguish disorder contributions from classical and
quantum-mechanical vibrational contributions. The analysis relies on
multitemperature (5-295 K) single-crystal neutron-diffraction data. Vibrational
frequencies extracted from the temperature dependence of the ADPs are in good
agreement with THz spectroscopic data. Aspects of the static disorder revealed
by this work, primarily tilting and displacement of the molecules, are compared
with corresponding results from previous, much more in-depth and time-consuming
Monte Carlo simulations; their salient findings are reproduced by this work,
demonstrating that the faster NCA approach provides reliable constraints for
the interpretation of diffuse scattering. The dielectric properties of PCNB can
thus be rationalized by an interpretation of the temperature-dependent ADPs in
terms of thermal motion and molecular disorder. The use of atomic displacement
parameters in the NCA approach is nonetheless hostage to reliable neutron data.
The success of this study demonstrates that state-of-the-art single-crystal
Laue neutron diffraction affords sufficiently fast the accurate data for this
type of study. In general terms, the validation of this work opens up the field
for numerous studies of solid-state molecular disorder in organic materials.Comment: Now published in Physical Review
Orbits of Globular Clusters in the Outer Galaxy: NGC 7006
We present a proper motion study of the distant globular cluster NGC 7006
based on the measurement of 25 photographic plates spanning a 40-year interval.
The absolute proper motion determined with respect to extragalactic objects is
(-0.96, -1.14) +- (0.35, 0.40) mas/yr. The total space velocity of NGC 7006 in
a Galactocentric rest frame is 279 km/s, placing the cluster on one of the most
energetic orbits (Ra =102 kpc) known to date for clusters within 40-kpc from
the Galactic center. We compare the orbits of four clusters that have
apocentric radii larger than 80 kpc (NGC 5466, NGC 6934, NGC 7006 and Pal 13)
with those of Galactic satellites with well-measured proper motions. These
clusters have orbits that are highly eccentric and of various inclinations with
respect to the Galactic plane. In contrast, the orbits of the Galactic
satellites are of low to moderate eccentricity and highly inclined. Based on
orbit types, chemical abundances and cluster parameters, we discuss the
properties of the hypothetical host systems of the remote globular clusters in
the Searle-Zinn paradigm. It is apparent that clusters such as NGC 5466, NGC
6934 and NGC 7006 formed in systems that more likely resemble the Fornax dSph,
rather than the Sagittarius dSph. We also discuss plausible causes for the
difference found so far between the orbit type of outer halo clusters and that
of Galactic satellites and for the tentative, yet suggestive phase-space
scatter found among outer halo clusters.Comment: 27 pages, 5 figures, to be published in the Astronomical Journa
HST astrometry in the 30 Doradus region: II. Runaway stars from new proper motions in the Large Magellanic Cloud
We present a catalog of relative proper motions for 368,787 stars in the 30
Doradus region of the Large Magellanic Cloud (LMC), based on a dedicated
two-epoch survey with the Hubble Space Telescope (HST) and supplemented with
proper motions from our pilot archival study. We demonstrate that a relatively
short epoch difference of 3 years is sufficient to reach a 0.1 mas
yr level of precision or better. A number of stars have relative proper
motions exceeding a 3-sigma error threshold, representing a mixture of Milky
Way denizens and 17 potential LMC runaway stars. Based upon 183 VFTS OB-stars
with the best proper motions, we conclude that none of them move faster than
0.3 mas yr in each coordinate -- equivalent to 70 km
s. Among the remaining 351 VFTS stars with less accurate proper motions,
only one candidate OB runaway can be identified. We rule out any OB star in our
sample moving at a tangential velocity exceeding 120 km s. The
most significant result of this study is finding 10 stars over wide range of
masses, which appear to be ejected from the massive star cluster R136 in the
tangential plane to angular distances from out to
, equivalent to 8-98 pc. The tangential velocities of these
runaways appear to be correlated with apparent magnitude, indicating a possible
dependence on the stellar mass.Comment: 45 pages (in referee format), 12 figures, 3 tables. Submitted to AJ.
Comments are welcom
Slow and fast dynamics in coupled systems: A time series analysis view
We study the dynamics of systems with different time scales, when access only
to the slow variables is allowed. We use the concept of Finite Size Lyapunov
Exponent (FSLE) and consider both the case when the equations of motion for the
slow components are known, and the situation when a scalar time series of one
of the slow variables has been measured. A discussion on the effects of
parameterizing the fast dynamics is given. We show that, although the
computation of the largest Lyapunov exponent can be practically infeasible in
complex dynamical systems, the computation of the FSLE allows to extract
information on the characteristic time and on the predictability of the
large-scale, slow-time dynamics even with moderate statistics and unresolved
small scales.Comment: 17 pages RevTeX, 6 PostScript figures, tarred, gzipped, uuencoded.
Submitted to Physica
State space description of national economies: the V4 countries
We present a new approach to description of national economies. For this we
use the state space viewpoint, which is used mostly in the theory of dynamical
systems and in the control theory. Gross domestic product, inflation, and
unemployment rates are taken as state variables. We demonstrate that for the
considered period of time the phase trajectory of each of the V4 countries
(Slovak Republic, Czech Republic, Hungary, and Poland) lies approximately in
one plane, so that the economic development of each country can be assocated
with a corresponding plane in the state space. The suggested approach opens a
way to a new set of economic indicators (for example, normal vectors of
national economies, various plane slopes, 2D angles between the planes
corresponding to different economies, etc.).
The tool used for computations is orthogonal regression (alias orthogonal
distance regression, alias total least squares method), and we also give
general arguments for using orthogonal regression instead of the classical
regression based on the least squares method.
A MATLAB routine for fitting 3D data to lines and planes in 3D is provided.Comment: 13 pages, 18 figure
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