Search results for "Ballistic"
showing 10 items of 49 documents
Prestretch potentiation of human skeletal muscle during ballistic movement
1981
The conditions associated prior to and during the transition from prestretch to shortening may have considerable influence on the final performance of muscle. In the present study male subjects of good physical condition performed vertical jumps on the force-platform with and without preliminary counter movement. In the counter movement jump (CMJ) the amplitude of the knee bending, velocity of the prestretch and the force attained at end of prestretch were the primary parameters of interest. In addition the coupling time indicating the transition from the eccentric (prestretch) phase to the concentric phase was recorded from the angular displacement and reaction force curves. In the final c…
The effects of a startle on awareness of action
2003
The execution of a ballistic movement within a reaction time task paradigm is significantly speeded up when an unexpected startling auditory stimulus (SAS) is delivered together with the imperative signal. Using Libet's clock, we investigated whether acceleration involves also the subjective appraisal of the time of task execution. In trials containing the SAS, reaction time shortened to 68.7% of control values. However, subjective judgment of task execution remained a similar time with respect to the imperative signal as in control trials. The dissociation between task execution and its subjective perception indicates the existence of separate circuits for action execution and action aware…
Relationship between isokinetic performance and ballistic movement
1983
The present experiments were carried out to assess the relationship between the mechanical behaviour of the leg extensor muscles in 12 male athletes during activities of a ballistic type and torque production, during: (1) torque production during isokinetic contraction: (2) ballistic type activities (vertical jumps from statis position = SJ, with counter-movement equal CMJ and after a fall from different heights equal DJ) and (3) a new anaerobic test (Bosco 1983a). This consisted of performing continuous jump work for a certain period of time (e.g., 60 s). Both ballistic activities and anaerobic power tests demonstrated the highest relationship with peak torques when this was developed resp…
Constraining the Pre-atmospheric Parameters of Large Meteoroids: Košice, a Case Study
2016
Out of a total around 50,000 meteorites currently known to science, the atmospheric passage was recorded instrumentally in only 25 cases with the potential to derive their atmospheric trajectories and pre-impact heliocentric orbits. Similarly, while observations of meteors generate thousands of new entries per month to existing databases, it is extremely rare they lead to meteorite recovery (http://www.meteoriteorbits.info/). These 25 exceptional cases thus deserve a thorough re-examination by different techniques—not only to ensure that we are able to match the model with the observations, but also to enable the best possible interpretation scenario and facilitate the robust extraction of …
The 15 March 2007 explosive crisis at Stromboli Volcano, Italy: assessing physical parameters through a multidisciplinary approach
2011
Basaltic volcanoes are dominated by lava emission and mild explosive activity. Nevertheless, many basaltic systems exhibit, from time to time, poorly documented and little-understood violent explosions. A short-lived, multiblast explosive crisis (paroxysmal explosion) occurred on 15 March 2007 during an effusive eruptive crisis at Stromboli (Italy). The explosive crisis, which started at 20:38:14 UT, had a total duration of ∼5 min. The combined use of multiparametric data collected by the permanent instrumental networks (seismic, acoustic, and thermal records) and a field survey carried out immediately after the event enabled us to constrain the eruptive dynamics and quantify physical param…
Time-dependent Landauer-Büttiker formula: Application to transient dynamics in graphene nanoribbons
2014
In this work we develop a time-dependent extension of the Landauer-B\"uttiker approach to study transient dynamics in time-dependent quantum transport through molecular junctions. A key feature of the approach is that it provides a closed integral expression for the time-dependence of the density matrix of the molecular junction after switch-on of a bias or gate potential which can be evaluated without the necessity of propagating individual single-particle orbitals. This allows for the study of time-dependent transport in large molecular systems coupled to wide band leads. As an application of the formalism we study the transient dynamics of zigzag and armchair graphene nanoribbons of diff…
Light Propagation in Heterogeneous Opal-Based Photonic Crystals
2006
Ballistic light propagation in the heterogeneous photonic crystals based on the thin triple-film opal have been studied in the wavelength range of low order photonic bandgaps. Since the scattered light experiences the diffraction attenuation, the spectra and the angle diagrams of the transmitted and forward scattered light have been used to identify the effect of heterostructuring.
Contribution to the development and the improvement of a digital model of the human body biofidelic HUByx by numerical methods for impact applications
2017
The study of human tolerance thresholds to impacts requires experiments on living or post mortem human subjects, which naturally raises ethical questions. To overcome these limitations, the development of numerical tools has led over the last few years to the implementation of numerical models more or less capable to accurately reproduce the mechanical behavior of the human body when subjected to various types of stresses. It is in this context that the numerical model HUByx (Hermaphrodite Biomechanics yx-model) has been developed within the research department COMM of the ICB lab at UTBM. This PhD work aims at validating and improving the biofidelity of the thoracic part of the HUByx model…
Internal photoemission in solar blind AlGaN Schottky barrier photodiodes
2005
We have analyzed the photoresponse of solar blind AlGaN Schottky barrier photodiodes below the alloy band gap energy, in the 3.5-4.5 eV range, and we show that it is dominated by internal photoemission. The n-type Schottky barrier height is shown to increase linearly with the band gap energy of the AlGaN alloy. The amplitude of the internal photoemission signal is about 20 times smaller than the value given by the Fowler theory based on a free electron model. We explain this result by taking into account the interband transitions and the ballistic transport of photoexcited electrons in the metal. This low value of internal photoemission allows us to achieve a spectral rejection ratio betwee…
The diffusion of carbon atoms inside carbon nanotubes
2008
We combine electron irradiation experiments in a transmission electron microscope with kinetic Monte Carlo simulations to determine the mobility of interstitial carbon atoms in single-walled carbon nanotubes. We measure the irradiation dose necessary to cut nanotubes repeatedly with a focused electron beam as a function of the separation between the cuts and at different temperatures. As the cutting speed is related to the migration of displaced carbon atoms trapped inside the tube and to their recombination with vacancies, we obtain information about the mobility of the trapped atoms and estimate their migration barrier to be about 0.25 eV. This is an experimental confirmation of the remar…