8,234 research outputs found
Quantization Noise Shaping for Information Maximizing ADCs
ADCs sit at the interface of the analog and digital worlds and fundamentally
determine what information is available in the digital domain for processing.
This paper shows that a configurable ADC can be designed for signals with non
constant information as a function of frequency such that within a fixed power
budget the ADC maximizes the information in the converted signal by frequency
shaping the quantization noise. Quantization noise shaping can be realized via
loop filter design for a single channel delta sigma ADC and extended to common
time and frequency interleaved multi channel structures. Results are presented
for example wireline and wireless style channels.Comment: 4 pages, 6 figure
A simple beam model for the shear failure of interfaces
We propose a novel model for the shear failure of a glued interface between
two solid blocks. We model the interface as an array of elastic beams which
experience stretching and bending under shear load and break if the two
deformation modes exceed randomly distributed breaking thresholds. The two
breaking modes can be independent or combined in the form of a von Mises type
breaking criterion. Assuming global load sharing following the beam breaking,
we obtain analytically the macroscopic constitutive behavior of the system and
describe the microscopic process of the progressive failure of the interface.
We work out an efficient simulation technique which allows for the study of
large systems. The limiting case of very localized interaction of surface
elements is explored by computer simulations.Comment: 11 pages, 13 figure
Local load sharing fiber bundles with a lower cutoff of strength disorder
We study the failure properties of fiber bundles with a finite lower cutoff
of the strength disorder varying the range of interaction between the limiting
cases of completely global and completely local load sharing. Computer
simulations revealed that at any range of load redistribution there exists a
critical cutoff strength where the macroscopic response of the bundle becomes
perfectly brittle, i.e. linearly elastic behavior is obtained up to global
failure, which occurs catastrophically after the breaking of a small number of
fibers. As an extension of recent mean field studies [Phys. Rev. Lett. 95,
125501 (2005)], we demonstrate that approaching the critical cutoff, the size
distribution of bursts of breaking fibers shows a crossover to a universal
power law form with an exponent 3/2 independent of the range of interaction.Comment: 4 pages, 4 figure
Damage in Fiber Bundle Models
We introduce a continuous damage fiber bundle model that gives rise to
macroscopic plasticity and compare its behavior with that of dry fiber bundles.
Several interesting constitutive behaviors are found in this model depending on
the value of the damage parameter and on the form of the disorder distribution.
In addition, we compare the behavior of global load transfer models with local
load transfer models and study in detail the damage evolution before failure.
We emphasize the analogies between our results and spinodal nucleation in
first-order phase transitions.Comment: 9 pages, 13 figures (ps, eps
Creep rupture of viscoelastic fiber bundles
We study the creep rupture of bundles of viscoelastic fibers occurring under
uniaxial constant tensile loading. A novel fiber bundle model is introduced
which combines the viscoelastic constitutive behaviour and the strain
controlled breaking of fibers. Analytical and numerical calculations showed
that above a critical external load the deformation of the system monotonically
increases in time resulting in global failure at a finite time , while
below the critical load the deformation tends to a constant value giving rise
to an infinite lifetime. Our studies revealed that the nature of the transition
between the two regimes, i.e. the behaviour of at the critical load
, strongly depends on the range of load sharing: for global load
sharing has a power law divergence at with a universal
exponent of 0.5, however, for local load sharing the transition becomes abrupt:
at the critical load jumps to a finite value, analogous to second and
first order phase transitions, respectively. The acoustic response of the
bundle during creep is also studied.Comment: 4 pages, 4 figures, APS style, submitted for publicatio
New universality class for the fragmentation of plastic materials
We present an experimental and theoretical study of the fragmentation of
polymeric materials by impacting polypropylene particles of spherical shape
against a hard wall. Experiments reveal a power law mass distribution of
fragments with an exponent close to 1.2, which is significantly different from
the known exponents of three-dimensional bulk materials. A 3D discrete element
model is introduced which reproduces both the large permanent deformation of
the polymer during impact, and the novel value of the mass distribution
exponent. We demonstrate that the dominance of shear in the crack formation and
the plastic response of the material are the key features which give rise to
the emergence of the novel universality class of fragmentation phenomena.Comment: 4 pages, 4 figures, appearing in Phys. Rev. Let
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