13,746 research outputs found
Interaction Grammars
Interaction Grammar (IG) is a grammatical formalism based on the notion of
polarity. Polarities express the resource sensitivity of natural languages by
modelling the distinction between saturated and unsaturated syntactic
structures. Syntactic composition is represented as a chemical reaction guided
by the saturation of polarities. It is expressed in a model-theoretic framework
where grammars are constraint systems using the notion of tree description and
parsing appears as a process of building tree description models satisfying
criteria of saturation and minimality
Articulatory optimisation in perturbed vowel articulation
A two-week perturbation EMA-experiment was carried out with palatal prostheses. Articulatory effort for five speakers was assessed by means of peak acceleration and jerk during the tongue tip gestures from /t/ towards /i, e, o, y, u/. After a period of no change speakers showed an increase in these values. Towards the end of the experiment the values decreased. The results are interpreted as three phases of carrying out changes in the internal model. At first, the complete production system is shifted in relation to the palatal change, afterwards speakers explore different production mechanisms which involves more articulatory effort. This second phase can be seen as a training phase where several articulatory strategies are explored. In the third phase speakers start to select an optimal movement strategy to produce the sounds so that the values decrease
The influence of the palate shape on articulatory token-to-token variability
Articulatory token-to-token variability not only depends on linguistic aspects like the phoneme inventory of a given language but also on speaker specific morphological and motor constraints. As has been noted previously (Perkell (1997), Mooshammer et al. (2004)) , speakers with coronally high "domeshaped" palates exhibit more articulatory variability than speakers with coronally low "flat" palates. One explanation for that is based on perception oriented control by the speaker. The influence of articulatory variation on the cross sectional area and consequently on the acoustics should be greater for flat palates than for domeshaped ones. This should force speakers with flat palates to place their tongue very precisely whereas speakers with domeshaped palates might tolerate a greater variability. A second explanation could be a greater amount of lateral linguo-palatal contact for flat palates holding the tongue in position. In this study both hypotheses were tested
A 3D biomechanical vocal tract model to study speech production control: How to take into account the gravity?
This paper presents a modeling study of the way speech motor control can deal
with gravity to achieve steady-state tongue positions. It is based on
simulations carried out with the 3D biomechanical tongue model developed at
ICP, which is now controlled with the Lambda model (Equilibrium-Point
Hypothesis). The influence of short-delay orosensory feedback on posture
stability is assessed by testing different muscle force/muscle length
relationships (Invariant Characteristics). Muscle activation patterns necessary
to maintain the tongue in a schwa position are proposed, and the relations of
head position, tongue shape and muscle activations are analyzed
Motor equivalent strategies in the production of /u/ in perturbed speech
Several articulatory strategies are available during the production of /u/, all resulting in a similar acoustic output. /u/ has two main constrictions, at the velum and at the lips. A perturbation of either constriction can be compensated at the other one, e.g wider constriction at the velum by more lip protrusion, wider lip opening by more tongue retraction. This study investigates whether speakers use this relation under perturbation. Six speakers were provided with palatal prostheses which were worn for two weeks. Speakers were instructed to make a serious attempt to produce normal speech. Their speech was recorded via EMA and acoustics several times over the adaptation period. Formant values of /u/-productions were measured. Velar constriction width and lip protrusion were estimated. For four speakers a correlation between constriction width and lip protrusion was found. A negative correlation between lip protrusion and F1 or F2 could sometimes be observed, but no correlation occurred between constriction size and either of the formants. The results show that under perturbation speakers use motor equivalent strategies in order to adapt. The correlation between constriction size and lip protrusion is stronger than in studies investigating unperturbed speech. This could be because under perturbation speakers are inclined to try out several strategies in order to reach the acoustic target and the co-variability might thus be greater
Explosive particle production in non-commutative inflation
We consider a model of inflation which has recently been proposed in the
literature and where inflation is induced by corrections to the energy density
coming from the non-commutativity of spacetime. We show that the very rapid
inflationary expansion typical of this model is responsible for a burst of
particle production which ends inflation and leads to a radiation-dominated
phase. We analytically estimate the energy density of these particles and we
confront the results with more precise numerical calculations. We estimate the
number of inflationary e-folds before the back-reaction of the radiation energy
density overcomes the non-commutative effects and terminate inflation
naturally.Comment: v2: minor typos corrected, one reference adde
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