16,523 research outputs found
"MADE IN ITALY" AND "MADE IN CHINA". EMPIRICAL ANALYSIS AND INDUSTRIAL POLICY IMPLICATIONS
quality, sectoral specialisation, international trade, price differentials
Technical quality assessment of an optoelectronic system for movement analysis
The Optoelectronic Systems (OS) are largely used in gait analysis to evaluate the motor performances of healthy subjects and patients. The accuracy of marker trajectories reconstruction depends on several aspects: the number of cameras, the dimension and position
of the calibration volume, and the chosen calibration procedure. In this paper we propose a methodology to evaluate the eects of the mentioned sources of error on the reconstruction of marker trajectories. The novel contribution of the present work consists in the dimension of the tested calibration volumes, which is comparable with the ones normally used in gait analysis; in addition, to simulate trajectories during clinical gait analysis, we provide non-default
paths for markers as inputs. Several calibration procedures are implemented and the same trial is processed with each calibration le, also considering dierent cameras congurations.
The RMSEs between the measured trajectories and the optimal ones are calculated for each comparison. To investigate the signicant dierences between the computed indices, an ANOVA analysis is implemented. The RMSE is sensible to the variations of the considered calibration volume and the camera congurations and it is always inferior to 43 mm
The effect of a nucleating agent on lamellar growth in melt-crystallizing polyethylene oxide
The effects of a (non co-crystallizing) nucleating agent on secondary
nucleation rate and final lamellar thickness in isothermally melt-crystallizing
polyethylene oxide are considered. SAXS reveals that lamellae formed in
nucleated samples are thinner than in the pure samples crystallized at the same
undercoolings. These results are in quantitative agreement with growth rate
data obtained by calorimetry, and are interpreted as the effect of a local
decrease of the basal surface tension, determined mainly by the nucleant
molecules diffused out of the regions being about to crystallize. Quantitative
agreement with a simple lattice model allows for some interpretation of the
mechanism.Comment: submitted to Journal of Applied Physics (first version on 22 Apr
2002
Thermoelectrics of Interacting Nanosystems -- Exploiting Superselection instead of Time-Reversal Symmetry
Thermoelectric transport is traditionally analyzed using relations imposed by
time-reversal symmetry, ranging from Onsager's results to fluctuation relations
in counting statistics. In this paper, we show that a recently discovered
duality relation for fermionic systems -- deriving from the fundamental
fermion-parity superselection principle of quantum many-particle systems --
provides new insights into thermoelectric transport. Using a master equation,
we analyze the stationary charge and heat currents through a weakly coupled,
but strongly interacting single-level quantum dot subject to electrical and
thermal bias. In linear transport, the fermion-parity duality shows that
features of thermoelectric response coefficients are actually dominated by the
average and fluctuations of the charge in a dual quantum dot system, governed
by attractive instead of repulsive electron-electron interaction. In the
nonlinear regime, the duality furthermore relates most transport coefficients
to much better understood equilibrium quantities. Finally, we naturally
identify the fermion-parity as the part of the Coulomb interaction relevant for
both the linear and nonlinear Fourier heat. Altogether, our findings hence
reveal that next to time-reversal, the duality imposes equally important
symmetry restrictions on thermoelectric transport. As such, it is also expected
to simplify computations and clarify the physical understanding for more
complex systems than the simplest relevant interacting nanostructure model
studied here.Comment: 38 pages (23 main paper, 15 appendix), 8 figure
Transits and Lensing by Compact Objects in the Kepler Field: Disrupted Stars Orbiting Blue Stragglers
Kepler's first major discoveries are two hot objects orbiting stars in its
field. These may be the cores of stars that have each been eroded or disrupted
by a companion star. The companion, which is the star monitored today, is
likely to have gained mass from its now-defunct partner, and can be considered
to be a blue straggler. KOI-81 is almost certainly the product of stable mass
transfer; KOI-74 may be as well, or it may be the first clear example of a blue
straggler created throughthree-body interactions.
We show that mass transfer binaries are common enough that Kepler should
discover ~1000 white dwarfs orbiting main sequence stars. Most, like KOI-74 and
KOI-81, will be discovered through transits, but many will be discovered
through a combination of gravitational lensing and transits, while lensing will
dominate for a subset. In fact, some events caused by white dwarfs will have
the appearance of "anti-transits" --i.e., short-lived enhancements in the
amount of light received from the monitored star. Lensing and other mass
measurements methods provide a way to distinguish white dwarf binaries from
planetary systems. This is important for the success of Kepler's primary
mission, in light of the fact that white dwarf radii are similar to the radii
of terrestrial planets, and that some white dwarfs will have orbital periods
that place them in the habitable zones of their stellar companions. By
identifying transiting and/or lensing white dwarfs, Kepler will conduct
pioneering studies of white dwarfs and of the end states of mass transfer. It
may also identify orbiting neutron stars or black holes. The calculations
inspired by the discovery of KOI-74 and KOI-81 have implications for
ground-based wide-field surveys as well as for future space-based surveys.Comment: 29 pages, 6 figures, 1 table; submitted to The Astrophysical Journa
CREEP OF CRACKED POLYMER FIBER REINFORCED CONCRETE UNDER SUSTAINED TENSILE LOADING
In fiber reinforced concrete (FRC), fibers are added to the fresh concrete mix in order to improve the residual tensile strength, the toughness and/or durability of a concrete element. Cur- rently, structural applications remain relatively scarce as the time-dependent behavior of FRC is still poorly understood. This paper reports the first results of an experimental campaign regarding the creep of cracked polymer FRC. In the test setup, cylindrical, notched FRC specimens are considered. The concrete is reinforced with structural polymeric fibers for use in load-bearing applications. In a first step, the material is characterized according to the European Standard EN14651. Secondly, the samples are precracked to localize the creep deformations and to monitor the crack growth in time. The samples are subjected to a sustained tensile load, whereby different load levels with respect to the individual residual strength are considered. The results of the first months of creep loading will be detailed and discussed in the paper
Slow-roll Inflation for Generalized Two-Field Lagrangians
We study the slow-roll regime of two field inflation, in which the two fields
are also coupled through their kinetic terms. Such Lagrangians are motivated by
particle physics and by scalar-tensor theories studied in the Einstein frame.
We compute the power spectra of adiabatic and isocurvature perturbations on
large scales to first order in the slow-roll parameters. We discuss the
relevance of the extra coupling terms for the amplitude and indexes of the
power spectra. Beyond the consistency condition which involves the amplitude of
gravitational waves, additional relations may be found in particular models
based on such Lagrangians: as an example, we find an additional general
consistency condition in implicit form for Brans-Dicke theory in the Einstein
frame.Comment: 17 pages, 1 figure, accepted for publication in Phys. Rev.
Quantification of habitat fragmentation reveals extinction risk in terrestrial mammals
Although habitat fragmentation is often assumed to be a primary driver of extinction, global patterns of fragmentation and its relationship to extinction risk have not been consistently quantified for any major animal taxon. We developed high-resolution habitat fragmentation models and used phylogenetic comparative methods to quantify the effects of habitat fragmentation on the world's terrestrial mammals, including 4,018 species across 26 taxonomic Orders. Results demonstrate that species with more fragmentation are at greater risk of extinction, even after accounting for the effects of key macroecological predictors, such as body size and geographic range size. Species with higher fragmentation had smaller ranges and a lower proportion of high-suitability habitat within their range, andmost high-suitability habitat occurred outside of protected areas, further elevating extinction risk. Our models provide a quantitative evaluation of extinction risk assessments for species, allow for identification of emerging threats in species not classified as threatened, and provide maps of global hotspots of fragmentation for the world's terrestrial mammals. Quantification of habitat fragmentation will help guide threat assessment and strategic priorities for global mammal conservation
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