1,999 research outputs found
Lagekostenbedrijf behaalt laag vervangingspercentage
In de praktijk blijkt de veevervanging op het Lagekostenbedrijf de nodige knelpunten op te leveren
Energy bursts in fiber bundle models of composite materials
As a model of composite materials, a bundle of many fibers with
stochastically distributed breaking thresholds for the individual fibers is
considered. The bundle is loaded until complete failure to capture the failure
scenario of composite materials under external load. The fibers are assumed to
share the load equally, and to obey Hookean elasticity right up to the breaking
point. We determine the distribution of bursts in which an amount of energy
is released. The energy distribution follows asymptotically a universal power
law , for any statistical distribution of fiber strengths. A similar
power law dependence is found in some experimental acoustic emission studies of
loaded composite materials.Comment: 5 pages, 4 fig
Discrete Fracture Model with Anisotropic Load Sharing
A two-dimensional fracture model where the interaction among elements is
modeled by an anisotropic stress-transfer function is presented. The influence
of anisotropy on the macroscopic properties of the samples is clarified, by
interpolating between several limiting cases of load sharing. Furthermore, the
critical stress and the distribution of failure avalanches are obtained
numerically for different values of the anisotropy parameter and as a
function of the interaction exponent . From numerical results, one can
certainly conclude that the anisotropy does not change the crossover point
in 2D. Hence, in the limit of infinite system size, the crossover
value between local and global load sharing is the same as the one
obtained in the isotropic case. In the case of finite systems, however, for
, the global load sharing behavior is approached very slowly
Failure avalanches in fiber bundles for discrete load increase
The statistics of burst avalanche sizes during failure processes in a
fiber bundle follows a power law, , for large avalanches.
The exponent depends upon how the avalanches are provoked. While it is
known that when the load on the bundle is increased in a continuous manner, the
exponent takes the value , we show that when the external load is
increased in discrete and not too small steps, the exponent value is
relevant. Our analytic treatment applies to bundles with a general probability
distribution of the breakdown thresholds for the individual fibers. The
pre-asymptotic size distribution of avalanches is also considered.Comment: 4 pages 2 figure
High power multi-color OPCPA source with simultaneous femtosecond deep-UV to mid-IR outputs
Many experimental investigations demand synchronized
pulses at various wavelengths, ideally with very short pulse
duration and high repetition rate. Here we describe a femtosecond
multi-color optical parametric chirped pulse amplifier
(OPCPA) with simultaneous outputs from the deep-UV to
the mid-IR with optical synchronization. The high repetition
rate of 160 kHz is well suited to compensate for low interaction
probability or low cross section in strong-field interactions.
Our source features high peak powers in the tens
to hundreds of MW regime with pulse durations below
110 fs, which is ideal for pump-probe experiments of nonlinear
and strong-field physics. We demonstrate its utility by
strong-field ionization experiments of xenon in the near- to
mid-IR.Peer ReviewedPostprint (published version
Phase transition in the modified fiber bundle model
We extend the standard fiber bundle model (FBM) with the local load sharing
in such a way that the conservation of the total load is relaxed when an
isolated fiber is broken. In this modified FBM in one dimension (1D), it is
revealed that the model exhibits a well-defined phase transition at a finite
nonzero value of the load, which is in contrast to the standard 1D FBM. The
modified FBM defined in the Watts-Strogatz network is also investigated, and
found is the existences of two distinct transitions: one discontinuous and the
other continuous. The effects of the long-range shortcuts are also discussed.Comment: 7 pages, to appear in Europhys. Let
High flux table-top soft X-ray source driven by sub-2-cycle, CEP stable, 1.85 μm 1 kHz pulses for carbon K-edge spectroscopy
We report on the first table-top high flux source of coherent soft X-ray radiation up to 400 eV, operating at 1 kHz. This source
covers the carbon K-edge with a beam brilliance of (4.3 ± 1.2) × 1015 photons/s/mm2/strad/10% bandwidth and a photon
flux of (1.9 ± 0.1) × 107 photons/s/1% bandwidth. We use this source to demonstrate table-top X-ray near edge fine structure
spectroscopy at the carbon K-edge of a polyimide foil and retrieve the specific absorption features corresponding to the
binding orbitals of the carbon atoms in the foil.Peer ReviewedPostprint (author's final draft
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