80 research outputs found
The effect of regular rhythm on the perception of linguistic and non-linguistic auditory input
First published: 30 October 2020Regular distribution of auditory stimuli over time can facilitate perception and attention.
However, such effects have to date only been observed in separate studies using
either linguistic or non-linguistic materials. This has made it difficult to compare
the effects of rhythmic regularity on attention across domains. The current study
was designed to provide an explicit within-subject comparison of reaction times and
accuracy in an auditory target-detection task using sequences of regularly and irregularly
distributed syllables (linguistic material) and environmental sounds (nonlinguistic
material). We explored how reaction times and accuracy were modulated
by regular and irregular rhythms in a sound- (non-linguistic) and syllable-monitoring
(linguistic) task performed by native Spanish speakers (N = 25). Surprisingly, we did
not observe that regular rhythm exerted a facilitatory effect on reaction times or accuracy.
Further exploratory analysis showed that targets that appear later in sequences
of syllables and sounds are identified more quickly. In late targets, reaction times
in stimuli with a regular rhythm were lower than in stimuli with irregular rhythm
for linguistic material, but not for non-linguistic material. The difference in reaction
times on stimuli with regular and irregular rhythm for late targets was also larger
for linguistic than for non-linguistic material. This suggests a modulatory effect of
rhythm on linguistic stimuli only once the percept of temporal isochrony has been established.
We suggest that temporal isochrony modulates attention to linguistic more
than to non-linguistic stimuli because the human auditory system is tuned to process
speech. The results, however, need to be further tested in confirmatory studies.This research was supported by the Spanish State Research
Agency through BCBL's Severo Ochoa excellence accreditation
SEV-2015-0490
Thixoforging tools materials: determination of appropriate features and experimental evaluation
Whereas thixoforming of low melting point alloys as aluminium or magnesium is
now an industrial reality, thixoforming of high melting point alloys, as steel, is still at the
research level. High working temperature, die wearing and production rate are problems that
must be solved and are under investigation. The aim of this work is to evaluate the thermal
and mechanical loadings applied to the tools during the steel thixoforging process in order to
determine if classical hot-work tool steel could be an appropriate tool material. This
evaluation has been realized thanks to experimental trials and to simulations on the finite
elements code Forge2009©. The effect of the loadings on the tool’s failure modes are
highlighted and compared to the ones observed in classical hot forging. Beyond this, the
failure modes of hot-work tool steel, the X38CrMoV5 or H11, is presented
Tooling materials and solutions for thixoforming steel
The aim of this work is to evaluate the thermal and mechanical loadings applied to
the tools during steel thixoforming process in order to determine appropriate tool materials
and solutions. This evaluation was realized thanks to experimental trials and to the finite
elements simulations. The effect of these loadings on the tool’s failure modes are highlighted
and compared to the ones observed in classical forming processes. Beyond this, the failure
modes of different tool materials and solutions are presented. The tested materials are hotworking
tool steels. Other possibilities and tool coating or surface treatments are discussed as
well
Characterisation of thermophysical properties of semi-solid steels for thixoforming
Major challenge for semi-solid processing includes broadening the range of alloys that can be successfully thixoformed and developing alloys specifically for thixoforming. One important parameter is appropriate solidus-liquidus interval. The wider the solidification interval, the wider the processing window. This study is related to the experimental determination of this critical parameter on eight different steel compositions. This parameter was obtained using Differential Scanning Calorimetry. This technique allows to obtain the solid fraction versus temperature. The paper also presents the results of thermophysical properties determination such as thermal diffusivity, heat capacity and thermal conductivity. These properties were measured from room temperature to semi-solid state in one particular steel. The thermal diffusivity was measured using the Laser Flash method and the heat capacity using a DSC calorimeter. The thermal conductivity was obtained by calculation knowing the thermal dilatation measured with a dilatometer. All these measurements were performed for temperatures up to the liquidus. These parameters are difficult to measure but they are important to determine for the conductive heating phase of a semi-solid forming (SSM) process.Peer reviewe
Improvement in Thixoforging of 7075 Aluminium Alloys at High Solid Fraction
peer reviewedThixoforging is a type of semi-solid metal processing at high solid fraction (0.5<1). 7075 aluminium alloys have been used as a feedstock for thixoforging in order to investigate thixoformability of a high performance aluminium alloy at high solid fraction. Higher solid fraction of 7075 alloy is less sensitive to temperature, avoids metal splash at high speed and allows laminar flow at high speed. Hot tool combined with lubricant tool coating are used to slow down the solidification rate of the high solid fraction metal by decreasing thermal exchanges with the tool. Improved thermal and forming parameters [1-2] will be applied to produce an automotive component by thixoforging and mechanical properties have been measured from tensile samples. High mechanical properties are obtained after T6 thermal treatment
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In situ study of granular micromechanics in semi-solid carbon steels
The granular micromechanics of semi-solid steel at ∼80% solid are studied by synchrotron radiography. A particulate soil mechanics approach to image analysis shows that deformation occurs by the translation and rotation of quasi-rigid grains under the action of contact forces, and that the changes in directional fabric and grain–grain contacts occur by mechanisms similar to those of highly compacted soils including “locked sands”. Grain-scale phenomena are then linked to the macroscopic displacement and strain fields and it is shown that shear-induced dilation is a fundamental response at both the grain and macro scales. Based on this, recommendations are made on future rheology experiments
Effect of Ga doping on magnetotransport properties in collosal magnetoresistive La0.7Ca0.3Mn1-xGaxO3 (0 < x < 0.1)
Samples of La0.7Ca0.3Mn1-xGaxO3 with x = 0, 0.025, 0.05 and 0.10 were
prepared by standard solid-state reaction. They were first characterized
chemically, including the microstructure. The magnetic properties and various
transport properties, i.e. the electrical resistivity, magnetoresistivity (for
a field below 8T), thermoelectric power and thermal conductivity measured each
time on the same sample, are reported. The markedly different behavior of the x
= 0.1 sample from those with a smaller Ga content, is discussed. The dilution
of the Mn3+/Mn4+ interactions with Ga doping considerably reduces the
ferromagnetic double exchange interaction within the manganese lattice leading
to a decrease of the Curie temperature. The polaron binding energy varies from
224 to 243 meV with increased Ga doping.Comment: submitted to J Magnet Magnet Mater; 13 figures; 2 tables; 38
reference
Tooling Materials and Solutions for Thixoforming of Steel
peer reviewedThe aim of this work is to evaluate the thermal and mechanical loadings applied to the
tools during steel thixoforming process in order to determine appropriate tool materials and
solutions. This evaluation was realized thanks to experimental trials and to the finite elements
simulations. The effect of these loadings on the tool’s failure modes are highlighted and compared
to the ones observed in classical forming processes. Beyond this, the failure modes of different tool
materials and solutions are presented. The tested materials are hot-working tool steels. Other
possibilities and tool coating or surface treatments are discussed as well
Study of liquid fraction evolution of semi-solid steels for thixoforming
peer reviewedMajor challenge for semi-solid processing includes broadening the range of alloys that can be successfully thixoformed and developing alloys specifically for thixoforming. One important parameter is appropriate solidus-liquidus interval. The wider the solidification interval, the wider the processing window.
This study is related to the experimental determination of this critical parameter on eight different steel compositions. This parameter was obtained using Differential Scanning Calorimetry. This technique allows to obtain the solid fraction versus temperature
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