1,137 research outputs found
Enhancing structural health monitoring with machine learning and data surrogates: a TCA-based approach for damage detection and localisation
This is the final version. Available from DEStech Publications via the DOI in this recordStructural health monitoring (SHM) involves constantly monitoring the condition of
structures to detect any damage or deterioration that might develop over time. Machine
learning methods have been successfully used in SHM, however, their effectiveness is
often limited by the availability of data for various damage cases. Such data can be
especially hard to obtain from high-value structures. In this paper, transfer component
analysis (TCA) with domain adaptation is utilised in conjunction with high-fidelity nu merical models to generate surrogates for damage identification without the requirement
for high volumes of data from various damaged states of the structure. The approach
is demonstrated on a laboratory structure, a nonlinear Brake-Reuß beam, where damage
scenarios correspond to different torque settings on a lap joint. It is shown that, in a
three-class scenario, machine learning algorithms can be trained using numerical data
and tested successfully on experimental data
Towards a generic test of the strong field dynamics of general relativity using compact binary coalescence: Further investigations
In this paper we elaborate on earlier work by the same authors in which a
novel Bayesian inference framework for testing the strong-field dynamics of
General Relativity using coalescing compact binaries was proposed. Unlike
methods that were used previously, our technique addresses the question whether
one or more 'testing coefficients' (e.g. in the phase) parameterizing
deviations from GR are non-zero, rather than all of them differing from zero at
the same time. The framework is well-adapted to a scenario where most sources
have low signal-to-noise ratio, and information from multiple sources as seen
in multiple detectors can readily be combined. In our previous work, we
conjectured that this framework can detect generic deviations from GR that can
in principle not be accomodated by our model waveforms, on condition that the
change in phase near frequencies where the detectors are the most sensitive is
comparable to that induced by simple shifts in the lower-order phase
coefficients of more than a few percent ( radians at 150 Hz). To
further support this claim, we perform additional numerical experiments in
Gaussian and stationary noise according to the expected Advanced LIGO/Virgo
noise curves, and coherently injecting signals into the network whose phasing
differs structurally from the predictions of GR, but with the magnitude of the
deviation still being small. We find that even then, a violation of GR can be
established with good confidence.Comment: 15 pages, 7 figures, Amaldi 9 proceeding
Metabolic design of macroscopic bioreaction models: application to Chinese hamster ovary cells
The aim of this paper is to present a systematic methodology to design macroscopic bioreaction models for cell cultures based upon metabolic networks. The cell culture is seen as a succession of phases. During each phase, a metabolic network represents the set of reactions occurring in the cell. Then, through the use of the elementary flux modes, these metabolic networks are used to derive macroscopic bioreactions linking the extracellular substrates and products. On this basis, as many separate models are obtained as there are phases. Then, a complete model is obtained by smoothly switching from model to model. This is illustrated with batch cultures of Chinese hamster ovary cells
A morphology-independent search for gravitational wave echoes in data from the first and second observing runs of Advanced LIGO and Advanced Virgo
Theoretical Physic
Towards a generic test of the strong field dynamics of general relativity using compact binary coalescence
Coalescences of binary neutron stars and/or black holes are amongst the most
likely gravitational-wave signals to be observed in ground based
interferometric detectors. Apart from the astrophysical importance of their
detection, they will also provide us with our very first empirical access to
the genuinely strong-field dynamics of General Relativity (GR). We present a
new framework based on Bayesian model selection aimed at detecting deviations
from GR, subject to the constraints of the Advanced Virgo and LIGO detectors.
The method tests the consistency of coefficients appearing in the waveform with
the predictions made by GR, without relying on any specific alternative theory
of gravity. The framework is suitable for low signal-to-noise ratio events
through the construction of multiple subtests, most of which involve only a
limited number of coefficients. It also naturally allows for the combination of
information from multiple sources to increase one's confidence in GR or a
violation thereof. We expect it to be capable of finding a wide range of
possible deviations from GR, including ones which in principle cannot be
accommodated by the model waveforms, on condition that the induced change in
phase at frequencies where the detectors are the most sensitive is comparable
to the effect of a few percent change in one or more of the low-order
post-Newtonian phase coefficients. In principle the framework can be used with
any GR waveform approximant, with arbitrary parameterized deformations, to
serve as model waveforms. In order to illustrate the workings of the method, we
perform a range of numerical experiments in which simulated gravitational waves
modeled in the restricted post-Newtonian, stationary phase approximation are
added to Gaussian and stationary noise that follows the expected Advanced
LIGO/Virgo noise curves.Comment: 26 pages, 23 figures, Accepted by PR
Population properties of compact objects from the second LIGO-Virgo gravitational-wave transient catalog
We report on the population of 47 compact binary mergers detected with a false-alarm rate of (BBH) population not discernible until now. First, the primary mass spectrum contains structure beyond a power law with a sharp high-mass cutoff; it is more consistent with a broken power law with a break at 39.7-+9.120.3 M? or a power law with a Gaussian feature peaking at 33.1-+5.64.0 M? (90% credible interval). While the primary mass distribution must extend to ~65 M? or beyond, only 2.9-+1.73.5% of systems have primary masses greater than 45 M?. Second, we find that a fraction of BBH systems have component spins misaligned with the orbital angular momentum, giving rise to precession of the orbital plane. Moreover,12%-44% of BBH systems have spins tilted by more than 90°, giving rise to a negative effective inspiral spin parameter, ceff. Under the assumption that such systems can only be formed by dynamical interactions, we infer that between 25% and 93% of BBHs with nonvanishing ceff| \u3e 0.01 are dynamically assembled. Third, we estimate merger rates, finding RBBH = 23.9-+8.614.3 Gpc-3 yr-1 for BBHs and RBNS = 320-+240490 Gpc-3 yr-1 for binary neutron stars. We find that the BBH rate likely increases with redshift (85% credibility) but not faster than the star formation rate (86% credibility). Additionally, we examine recent exceptional events in the context of our population models, finding that the asymmetric masses of GW190412 and the high component masses of GW190521 are consistent with our models, but the low secondary mass of GW190814 makes it an outlier
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All-sky search for short gravitational-wave bursts in the second Advanced LIGO and Advanced Virgo run
We present the results of a search for short-duration gravitational-wave transients in the data from the second observing run of Advanced LIGO and Advanced Virgo. We search for gravitational-wave transients with a duration of milliseconds to approximately one second in the 32-4096 Hz frequency band with minimal assumptions about the signal properties, thus targeting a wide variety of sources. We also perform a matched-filter search for gravitational-wave transients from cosmic string cusps for which the waveform is well modeled. The unmodeled search detected gravitational waves from several binary black hole mergers which have been identified by previous analyses. No other significant events have been found by either the unmodeled search or the cosmic string search. We thus present the search sensitivities for a variety of signal waveforms and report upper limits on the source rate density as a function of the characteristic frequency of the signal. These upper limits are a factor of 3 lower than the first observing run, with a 50% detection probability for gravitational-wave emissions with energies of ∼10-9 Mc2 at 153 Hz. For the search dedicated to cosmic string cusps we consider several loop distribution models, and present updated constraints from the same search done in the first observing run
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