15,723 research outputs found
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A mission synthesis algorithm for fatigue damage analysis
This paper presents a signal processing based algorithm, the Mildly Nonstationary Mission Synthesis
(MNMS), which produces a short mission signal from long records of experimental data. The
algorithm uses the Discrete Fourier Transform, Orthogonal Wavelet Transform and bump reinsertion
procedures. In order to observe the algorithm effectiveness a fatigue damage case study was
performed for a vehicle lower suspension arm using signals containing tensile and compressive
preloading. The mission synthesis results were compared to the original road data in terms of both the
global signal statistics and the fatigue damage variation as a function of compression ratio. Three
bump reinsertion methods were used and evaluated. The methods differed in the manner in which
bumps (shock events) from different wavelet groups (frequency bands) were synchronised during the
reinsertion process. One method, based on time synchronised section reinsertion, produced the best
results in terms of mission signal kurtosis, crest factor, root-mean-square level and power spectral
density. For improved algorithm performance, bump selection was identified as the main control
parameter requiring optimisation
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A mission synthesis algorithm for editing variable amplitude fatigue signals
This paper presents a wavelet-based fatigue data editing algorithm, known
as Wavelet Bump Extraction (WBE), to summarise long record of fatigue
loadings. The key point of this algorithm is to produce a shorter time
history (mission signal) that retains the majority of the original fatigue
damage whilst preserving cycle sequence information. In WBE, features
or bumps are identified in characteristic frequency bands using the
Daubechies’ wavelet transform. Comparison of the fatigue life between
the original and mission signals was performed to validate the algorithm.
The fatigue life was predicted using a variable amplitude fatigue damage
model and the results showed a good correlation between the damage
caused by the original and mission signals. Finally, the findings suggest
that WBE is a suitable approach for producing a shortened mission signal for accelerated fatigue testing
On some aspects of the noise propagation from supersonic aircraft
The noise problem associated with an aircraft flying at supersonic speeds is shown to depend primarily on the shock wave pattern formed by the aircraft. The noise intensity received by a ground observer from a supersonic aircraft flying at high as well as low altitudes, is shown to be high although it is of a transient nature. Continues
Mapping CS in Starburst Galaxies: Disentangling and Characterising Dense Gas
Aims. We observe the dense gas tracer CS in two nearby starburst galaxies to
determine how the conditions of the dense gas varies across the circumnuclear
regions in starburst galaxies. Methods. Using the IRAM-30m telescope, we mapped
the distribution of the CS(2-1) and CS(3-2) lines in the circumnuclear regions
of the nearby starburst galaxies NGC 3079 and NGC 6946. We also detected the
formaldehyde (H2CO) and methanol (CH3OH) in both galaxies. We marginally detect
the isotopologue C34S. Results. We calculate column densities under LTE
conditions for CS and CH3OH. Using the detections accumulated here to guide our
inputs, we link a time and depth dependent chemical model with a molecular line
radiative transfer model; we reproduce the observations, showing how conditions
where CS is present are likely to vary away from the galactic centres.
Conclusions. Using the rotational diagram method for CH3OH, we obtain a lower
limit temperature of 14 K. In addition to this, by comparing the chemical and
radiative transfer models to observations, we determine the properties of the
dense gas as traced by CS (and CH3OH). We also estimate the quantity of the
dense gas. We find that, provided that there are a between 10^5 and 10^6 dense
cores in our beam, for both target galaxies, emission of CS from warm (T = 100
- 400 K), dense (n(H2) = 10^5-6 cm-3) cores, possibly with a high cosmic ray
ionisation rate (zeta = 100 zeta0) best describes conditions for our central
pointing. In NGC 6946, conditions are generally cooler and/or less dense
further from the centre, whereas in NGC 3079, conditions are more uniform. The
inclusion of shocks allows for more efficient CS formation, leading to an order
of magnitude less dense gas being required to replicate observations in some
cases.Comment: 14 pages, 10 figures, accepted to A&
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Flourishing Fashion
Little research has been conducted into the relationship between fashion and psychology, even less on how individuals create wellbeing through appearance and clothing. In this study, the subjective experience of wearing an “outfit that makes you happy” was analyzed using interpretive phenomenological analysis (IPA). Six participants, both male and female, were interviewed wearing an outfit that “made them happy.” The semi-structured interviews highlighted the importance of “intentionally managing identity.” Analysis found subordinate themes: shaping identity, coping strategies, and social identity. These were broken down into “knowing who I am,” “matching my outsides to my insides,” “creating my best self,” “managing moods,” “resilience,” “fashioning positive relationships,” and “shared values,” and linked to the concept of flourishing in positive psychology (PP). The results suggest that how the participants dress plays an active part in their wellbeing through expressing positive emotions, engagement, relationships, meaning, and accomplishment (PERMA)
Quasiparticle relaxation in optically excited high-Q superconducting resonators
The quasiparticle relaxation time in superconducting films has been measured
as a function of temperature using the response of the complex conductivity to
photon flux. For tantalum and aluminium, chosen for their difference in
electron-phonon coupling strength, we find that at high temperatures the
relaxation time increases with decreasing temperature, as expected for
electron-phonon interaction. At low temperatures we find in both
superconducting materials a saturation of the relaxation time, suggesting the
presence of a second relaxation channel not due to electron-phonon interaction.Comment: 4 pages, 3 figure
Reconciling transport models across scales: the role of volume exclusion
Diffusive transport is a universal phenomenon, throughout both biological and
physical sciences, and models of diffusion are routinely used to interrogate
diffusion-driven processes. However, most models neglect to take into account
the role of volume exclusion, which can significantly alter diffusive
transport, particularly within biological systems where the diffusing particles
might occupy a significant fraction of the available space. In this work we use
a random walk approach to provide a means to reconcile models that incorporate
crowding effects on different spatial scales. Our work demonstrates that
coarse-grained models incorporating simplified descriptions of excluded volume
can be used in many circumstances, but that care must be taken in pushing the
coarse-graining process too far
Enhancement of quasiparticle recombination in Ta and Al superconductors by implantation of magnetic and nonmagnetic atoms
The quasiparticle recombination time in superconducting films, consisting of
the standard electron-phonon interaction and a yet to be identified low
temperature process, is studied for different densities of magnetic and
nonmagnetic atoms. For both Ta and Al, implanted with Mn, Ta and Al, we observe
an increase of the recombination rate. We conclude that the enhancement of
recombination is not due to the magnetic moment, but arises from an enhancement
of disorder.Comment: 4 pages, 4 figure
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