10,605 research outputs found
Phonological category quality in the mental lexicon of child and adult learners
• Aims and Objectives: The aim was to identify which criteria children used to decide on the category membership of native and non-native vowels, and to get insight into the organization of phonological representations in the bilingual mind.
• Methodology: The study consisted of two cross-language mispronunciation detection tasks, in which L2 vowels were inserted in L1 words, and vice versa. In Experiment 1, 9-12-year-old Dutch-speaking children were presented with Dutch words which were either pronounced with the target Dutch vowel or with an English vowel inserted in the Dutch consonantal frame. Experiment 2 was a mirror of the first, with English words which were pronounced ‘correctly’ or which were ‘mispronounced’ with a Dutch vowel.
• Data and Analysis: It was examined to what extent child and adult listeners accepted substitutions of Dutch vowels by English ones, and vice versa, and which vowel substitutions were accepted or rejected.
• Findings: The results of Experiment 1 revealed that at that age children have well-established phonological vowel categories in their native language. However, Experiment 2 showed that in the non-native language, children tended to accept mispronounced items which involve sounds from their native language. At the same time, though, they did fully rely on their native phonemic inventory because the children accepted most of the correctly pronounced English items.
• Originality: While many studies have examined native and non-native perception by infants, studies on first and second language perception of school-age children are rare. This study adds to the body of literature aimed at expanding our knowledge in this area.
• Implications: The study has implications for models of the organization of the bilingual mind: while proficient adult non-native listeners generally have clearly separated sets of phonological representations for their two languages, for non-proficient child learners, the L1 phonology still exerts a big influence on the L2 phonology
Renormalization group coefficients and the S-matrix
We show how to use on-shell unitarity methods to calculate renormalization
group coefficients such as beta functions and anomalous dimensions. The central
objects are the form factors of composite operators. Their discontinuities can
be calculated via phase-space integrals and are related to corresponding
anomalous dimensions. In particular, we find that the dilatation operator,
which measures the anomalous dimensions, is given by minus the phase of the
S-matrix divided by pi. We illustrate our method using several examples from
Yang-Mills theory, perturbative QCD and Yukawa theory at one-loop level and
beyond.Comment: 25 pages, 4 figures; v2: explanations improved, references added,
matches journal versio
Charging changes contact composition in binary sphere packings
Equal volume mixtures of small and large polytetrafluorethylene (PTFE)
spheres are shaken in an atmosphere of controlled humidity which allows to also
control their tribo-charging. We find that the contact numbers are
charge-dependent: as the charge density of the beads increases, the number of
same-type contacts decreases and the number of opposite-type contacts
increases. This change is not caused by a global segregation of the sample.
Hence, tribo-charging can be a way to tune the local composition of a granular
material.Comment: 7 Pages, 5 Figure
A Low-Power CoAP for Contiki
Internet of Things devices will by and large
be battery-operated, but existing application protocols
have typically not been designed with power-efficiency in
mind. In low-power wireless systems, power-efficiency is
determined by the ability to maintain a low radio duty
cycle: keeping the radio off as much as possible. We
present an implementation of the IETF Constrained
Application Protocol (CoAP) for the Contiki operating system
that leverages the ContikiMAC low-power duty cycling
mechanism to provide power efficiency. We experimentally
evaluate our low-power CoAP, demonstrating that an
existing application layer protocol can be made power-efficient
through a generic radio duty cycling mechanism.
To the best of our knowledge, our CoAP implementation is
the first to provide power-efficient operation through radio
duty cycling. Our results question the need for specialized
low-power mechanisms at the application layer, instead
providing low-power operation only at the radio duty
cycling layer
Classical and numerical approaches to determining V-section band clamp axial stiffness
V-band clamp joints are used in a wide range of applications to connect circular flanges, for ducts, pipes and the turbocharger housing. Previous studies and research on V-bands are either purely empirical or analytical with limited applicability on the variety of V-band design and working conditions. In this paper models of the V-band are developed based on the classical theory of solid mechanics and the finite element method to study the behaviour of the V-bands under axial loading conditions. The good agreement between results from the developed FEA and the classical model support the suitability of the latter to model V-band joints with diameters greater than 110 mm under axial loading. The results from both models suggest that the axial stiffness for this V-band cross section reaches a peak value for V-bands with radius of approximately 150 mm across a wide range of coefficients of friction. Also, it is shown that the coefficient of friction and the wedge angle have a significant effect on the axial stiffness of V-bands
Topological Order and Quantum Criticality
In this chapter we discuss aspects of the quantum critical behavior that
occurs at a quantum phase transition separating a topological phase from a
conventionally ordered one. We concentrate on a family of quantum lattice
models, namely certain deformations of the toric code model, that exhibit
continuous quantum phase transitions. One such deformation leads to a
Lorentz-invariant transition in the 3D Ising universality class. An alternative
deformation gives rise to a so-called conformal quantum critical point where
equal-time correlations become conformally invariant and can be related to
those of the 2D Ising model. We study the behavior of several physical
observables, such as non-local operators and entanglement entropies, that can
be used to characterize these quantum phase transitions. Finally, we briefly
consider the role of thermal fluctuations and related phase transitions, before
closing with a short overview of field theoretical descriptions of these
quantum critical points.Comment: 24 pages, 7 figures, chapter of the book "Understanding Quantum Phase
Transitions", edited by Lincoln D. Carr (CRC Press / Taylor and Francis,
2010); v2: updated reference
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