The Phonetics of Speech Production and Medical Research

The production of speech requires the interplay of a number of cognitive and motoric activities, which make it an interesting object of study from both a linguistic and a medical point of view. In this paper, we discuss, first, the features and domain of application of the most used technologies in linguistic research on speech production, focusing on those that have been applied to medicine. Second, we offer an insight into the main results that have been obtained so far in studying dysarthria in Italian Parkinson's Disease, as an example of the interdisciplinary, experimental research at the border between linguistics and medicine

Tunneling-percolation origin of nonuniversality: theory and experiments

A vast class of disordered conducting-insulating compounds close to the percolation threshold is characterized by nonuniversal values of transport critical exponent t, in disagreement with the standard theory of percolation which predicts t = 2.0 for all three dimensional systems. Various models have been proposed in order to explain the origin of such universality breakdown. Among them, the tunneling-percolation model calls into play tunneling processes between conducting particles which, under some general circumstances, could lead to transport exponents dependent of the mean tunneling distance a. The validity of such theory could be tested by changing the parameter a by means of an applied mechanical strain. We have applied this idea to universal and nonuniversal RuO2-glass composites. We show that when t > 2 the measured piezoresistive response \Gamma, i. e., the relative change of resistivity under applied strain, diverges logarithmically at the percolation threshold, while for t = 2, \Gamma does not show an appreciable dependence upon the RuO2 volume fraction. These results are consistent with a mean tunneling dependence of the nonuniversal transport exponent as predicted by the tunneling-percolation model. The experimental results are compared with analytical and numerical calculations on a random-resistor network model of tunneling-percolation.Comment: 13 pages, 12 figure

Acquisizione delle vocali L2 dell’inglese americano da parte di apprendenti italofoni: un confronto tra training percettivo e training articolatorio con ecografo

La realizzazione del contrasto vocalico dell’inglese americano /ɑ-ʌ/ (es. cop-cup) da parte di apprendenti italofoni risulta essere particolarmente difficile in produzione, poiché le differenze fonetiche-fonologiche dei due sistemi linguistici e le regole di conversione grafema-fonema fanno sì che gli apprendenti italofoni realizzino il contrasto L2-/ɑ-ʌ/ utilizzando le vocali native /ɔ-a/ rispettivamente. Lo scopo di questo studio è quello di osservare se un breve training possa aiutare gli apprendenti italofoni a migliorare la produzione delle vocali non native /ɑ-ʌ/. In particolare, si effettuerà un confronto tra un training percettivo e un training articolatorio, effettuato con l’utilizzo di un ecografo, al fine di osservare: 1) gli effetti di entrambi i training sulla realizzazione del contrasto L2 /ɑ-ʌ/; e 2) se il training articolatorio comporti risultati migliori rispetto a quello percettivo. Allo studio hanno partecipato nove studentesse salentine che sono state suddivise, in modo casuale, in tre gruppi: i) tre soggetti hanno preso parte al training percettivo della durata di un’ora (ES-P): ii) tre soggetti hanno partecipato al training articolatorio con ultrasuono della durata di un’ora (ES-US); iii) tre soggetti di controllo che non hanno effettuato alcun tipo di training (CS). I primi due gruppi (ES-P e ES-US) hanno ricevuto istruzioni sulle caratteristiche fonetiche sia delle vocali L2 /ɑ-ʌ/ che delle vocali della L1 /ɔ-a/ nonché sulle loro differenze utilizzando una rappresentazione sul piano cartesiano delle formanti F1 e F2. Successivamente, ciascun gruppo ha effettuato il training: i) i soggetti del gruppo ES-P hanno effettuato un test di identificazione basato sulla procedura High Variability Phonetic Training; ii) i soggetti del gruppo ES-US hanno effettuato un training articolatorio osservando sia un video relativo ai gesti linguali durante la produzione delle vocali /ɑ-ʌ/ da parte di un parlante nativo, sia una visualizzazione dinamica dei movimenti e della posizione della lingua, ottenuta grazie ad una sonda ecografica posizionata sotto il proprio mento. Le partecipanti sono state registrate sia prima che dopo l’addestramento (pre- e post-test) e le loro produzioni sono state analizzate acusticamente misurando il valore delle prime due formanti. I risultati mostrano che nel pre-test tutti le apprendenti realizzano L2-/ɑ-ʌ/ come L1-/ɔ-a/ rispettivamente. Al contrario, nel post-test sono soprattutto le apprendenti che hanno effettuato il training articolatorio riescono a realizzare le vocali L2 in modo differente sia rispetto a quelle realizzate nel pre-test sia rispetto alle vocali della L1. In particolare, un’apprendente produce entrambe le vocali non native in modo più accurato. Il training articolatorio sembra quindi essere più efficace del training percettivo.

Study of electrical properties of piezoresistive pastes and determination of the electrical transport

A vast class of disordered conducting-insulating compounds close to the percolation threshold is characterized by nonuniversal values of transport critical exponents. The lack of universality implies that critical indexes may depend on material properties such as microstructure, composition etc., and that in principle they can be influenced by suitable applied perturbations leading to important informations about the origin of nonuniversality. Here we show that RuO2-glass compounds can have nonuniversal values of transport critical exponents which can be altered by an applied mechanical strain leading to a logarithmically divergent piezoresistive response at the percolation threshold. This finding supports the tunneling-percolation theory of nonuniversality proposed several years ago

Transport nonuniversality and critical behavior of the piezoresistive response in thick-film resistors

Thick-film resistors (TFRs) consist of a percolating network of conducting oxide nanoparticlesdispersed in an insulating glassy matrix, whose resistive properties are dominated by quantumtunneling across insulating layers separating adjacent conducting grains. Tunneling processes are at the origin of the high sensitivity of the TFRs resistances to applied strains. We have measuredtransport and piezoresistive response for different RuO2-based TFRs as a function of metallic concentration x and RuO 2 grain sizes. The conductivity is shown to vanish as x approaches a criticalconcentration xc by following a power law with nonuniversal critical exponents, while thepiezoresistivity diverges at the same critical concentration. We argue that nonuniversality and diverging piezoresistivity have the same origin and arise from the highly fluctuation inter-graintunneling distances determined by the segregated microstructure of TFRs

Strain modulation of transport criticality in RuO2-based thick-film resistors

We show that in RuO2–glass composites the nonuniversal resistivity exponent can be modulated by an applied mechanical strain, signaled by a logarithmic divergence of the piezoresistive response at the percolation threshold. We interpret this phenomenon as being due to a tunneling-distance dependence of the transport exponent, supporting therefore a theory of transport nonuniversality proposed some years ago. © 2004 American Institute of Physics. [DOI: 10.1063/1.1835996

Nano grain thick-film pastes for mechanical sensor applications

Project aim: optimised piezoresistive thick-film compositions, especially for low-temperature applications on aluminum alloys, titanium alloys, steel and glas

Low-temperature thick-film systems for electronic and sensor applications

This paper presents recent work on complete thick-film systems, including dielectrics, conductors and resistors, with a lowered firing temperature range of 450...750°C. These materials allow the extension of proven, reliable and inexpensive thick-film technology to novel applications in electronics and sensors