176 research outputs found
Single-particle model for a granular ratchet
A simple model for a granular ratchet corresponding to a single grain
bouncing off a vertically vibrating sawtooth-like base is studied. Depending on
the vibration strength, the sawtooth roughness and the restitution coefficient,
horizontal transport in both the preferred and unfavoured directions is
observed. A phase diagram indicating the regions in parameter space where each
of the three possible regimes (no current, normal current, and current
reversal) occurs is presented.Comment: 7 pages, 3 figures, submitted to Physica
Avalanches in the Weakly Driven Frenkel-Kontorova Model
A damped chain of particles with harmonic nearest-neighbor interactions in a
spatially periodic, piecewise harmonic potential (Frenkel-Kontorova model) is
studied numerically. One end of the chain is pulled slowly which acts as a weak
driving mechanism. The numerical study was performed in the limit of infinitely
weak driving. The model exhibits avalanches starting at the pulled end of the
chain. The dynamics of the avalanches and their size and strength distributions
are studied in detail. The behavior depends on the value of the damping
constant. For moderate values a erratic sequence of avalanches of all sizes
occurs. The avalanche distributions are power-laws which is a key feature of
self-organized criticality (SOC). It will be shown that the system selects a
state where perturbations are just able to propagate through the whole system.
For strong damping a regular behavior occurs where a sequence of states
reappears periodically but shifted by an integer multiple of the period of the
external potential. There is a broad transition regime between regular and
irregular behavior, which is characterized by multistability between regular
and irregular behavior. The avalanches are build up by sound waves and shock
waves. Shock waves can turn their direction of propagation, or they can split
into two pulses propagating in opposite directions leading to transient
spatio-temporal chaos. PACS numbers: 05.70.Ln,05.50.+q,46.10.+zComment: 33 pages (RevTex), 15 Figures (available on request), appears in
Phys. Rev.
Agrupamento de modelos de regressão da análise de adaptabilidade e estabilidade de genótipos
Enzymatic removal of cellulose from cotton/polyester fabric blends
The production of light-weight polyester fabrics from a polyester/cotton blended fabric, by means of the enzymatic removal of the cellulosic part of the material, was investigated. The removal of cotton from the
blended fabric yielded more than 80% of insoluble microfibrillar material by the combined action of high beating effects and cellulase hydrolysis.Other major features of this enzymatic process for converting cotton fibers into microfibrillar material are bath ratio, enzyme dosage and treatment time
Hemograma, bioquímica sérica e histologia da biópsia hepática de bovinos após administração de polpa cítrica
Adrenal glands of Spix's yellow-toothed cavy (Galea spixii, Wagler, 1831): morphological and morphometric aspects
Relationship between total bacteria counts and somatic cell counts from mammary quarters infected by mastitis pathogens
Geological investigation of the central portion of the Santa Marta impact structure, Piauí State, Brazil
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