107 research outputs found
Determination of the universality class of crystal plasticity
Although scaling phenomena have long been documented in crystalline
plasticity, the universality class has been difficult to identify due to the
rarity of avalanche events, which require large system sizes and long times in
order to accurately measure scaling exponents and functions. Here we present
comprehensive simulations of two-dimensional dislocation dynamics under shear,
using finite-size scaling to extract scaling exponents and the avalanche
profile scaling function from time-resolved measurements of slip-avalanches.
Our results provide compelling evidence that both the static and dynamic
universality classes are consistent with the mean-field interface depinning
model.Comment: 6 pages, 4 figures. Figure 4 inset has been corrected as compared to
the EPL publication. We thank Michael Zaiser for bringing its incorrect
caption to our attention. The correction leaves all results unaffecte
Jamming Criticality of Near-Crystals
We report on the critical properties of minimaly-polydisperse crystals,
hexagonal in 2d and face-centered cubic in 3 dimensions, at the isostatic
jamming point. The force and gap distributions display power-law tails for
small values. The vibrational density of states (VDOS) is flat. The scaling
behavior of forces of extended floppy modes and the VDOS are universal and in
agreement with an infinite-dimensional mean-field theory and maximally
amorphous packings down to 2 dimensions. The distributions of gaps and forces
of localized floppy modes of near-crystals appear non-universal. A small
fraction of normal modes exhibit partial localization at low frequency. The
majority of normal modes is delocalized exhibiting a characteristic inverse
participation ratio scaling with frequency. The packing fraction and order at
jamming decay linearly and quadratically respectively with polydispersity down
to the maximally amorphous state.Comment: main text 5 pages, 7 figures. Supplementary material included in the
en
Chemical species tomographic imaging of the vapour fuel distribution in a compression-ignition engine
This article reports the first application of chemical species tomography to visualise the in-cylinder fuel vapour concentration distribution during the mixing process in a compression-ignition engine. The engine was operated in motored conditions using nitrogen aspiration and fired conditions using a gasoline-like blend of 50% iso-dodecane and 50% n-dodecane. The tomography system comprises 31 laser beams arranged in a co-planar grid located below the injector. A novel, robust data referencing scheme was employed to condition the acquired data for image reconstruction using the iterative Landweber algorithm. Tomographic images were acquired during the compression stroke at a rate of 13 frames per crank angle degree within the same engine cycle at 1200 r min−1. The temperature-dependent fuel evaporation rate and mixing evolution were observed at different injection timings and intake pressure and temperature conditions. An initial cross-validation of the tomographic images was performed with planar laser-induced fluorescence images, showing good agreement in feature localisation and identification. This is the first time chemical species tomography using near-infrared spectroscopic absorption has been validated under engine conditions, and the first application of chemical species tomography to a compression-ignition engine
Analog-Signal Quality Characterization of the FLITES Distributed 192-Channel Data Acquisition System
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