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Nous abordons la question de l'éducation des enfants sourds à travers un ensemble de regards croisés. L'approche adoptée tout au long de cette recherche se situe au carrefour de la sociolinguistique et de la didactique du plurilinguisme et emprunte essentiellement aux derniers développements de ces deux disciplines tentant ainsi de renouveler le questionnement sur l'enfant sourd et ses langues. <br />Dans un premier volet de la thèse, à travers une perspective sociolinguistique, il s'agit de prendre en compte : <br />-les dimensions sociales et institutionnelles de la surdité afin de cerner diachroniquement et synchroniquement la place accordée à chacune des langues (français/LSF) dans la scolarisation des enfants sourds ;<br />-les représentations sociales véhiculées par des discours d'enseignants travaillant avec des enfants sourds dans des classes spécialisées.<br />Dans un second volet de cette recherche, la perspective est socio-didactique et présente une étude micro-sociolinguistique des interactions de classe qui explore plus particulièrement les jeux et les enjeux des langues et autres codes présents dans l'espace scolaire.<br />La finalité de la recherche est double : faire avancer la connaissance d'une situation de bilinguisme particulière, et encore mal connue, et contribuer à proposer des pistes de réflexions ouvrant des perspectives dans l'intervention éducative auprès des enfants sourds.

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In this diploma thesis were created voice activity detectors according to the standard ITU-T G.729 and G.723.1. The voice activity detectors were implements in the digital signal processor TMS320C6416 made by Texas Instruments. At the same time detectors were designed using by MATLAB programming language. The diploma thesis can be divided into two parts. In the theoretical section provides information on how to report detectors in the standard ITU-T G.729 and G.723.1. In the implementation part is described steps in the implementation of the detector in signal processor TMS320C6416 and there are discussed various differences compared to the documentation.

Although vector quantization (VQ) is an established topic in communication, its practical utility has been limited due to (i) prohibitive complexity for higher quality and bit-rate, (ii) structured VQ methods which are not analyzed for optimum performance, (iii) difficulty of mapping theoretical performance of mean square error (MSE) to perceptual measures. However, an ever increasing demand for various source signal compression, points to VQ as the inevitable choice for high efficiency. This thesis addresses all the three above issues, utilizing the power of parametric stochastic modeling of the signal source, viz., Gaussian mixture model (GMM) and proposes new solutions. Addressing some of the new requirements of source coding in network applications, the thesis also presents solutions for scalable bit-rate, rate-independent complexity and decoder scalability. While structured VQ is a necessity to reduce the complexity, we have developed, analyzed and compared three different schemes of compensation for the loss due to structured VQ. Focusing on the widely used methods of split VQ (SVQ) and KLT based transform domain scalar quantization (TrSQ), we develop expressions for their optimum performance using high rate quantization theory. We propose the use of conditional PDF based SVQ (CSVQ) to compensate for the split loss in SVQ and analytically show that it achieves coding gain over SVQ. Using the analytical expressions of complexity, an algorithm to choose the optimum splits is proposed. We analyze these techniques for their complexity as well as perceptual distortion measure, considering the specific case of quantizing the wide band speech line spectrum frequency (LSF) parameters. Using natural speech data, it is shown that the new conditional PDF based methods provide better perceptual distortion performance than the traditional methods. Exploring the use of GMMs for the source, we take the approach of separately estimating the GMM parameters and then use the high rate quantization theory in a simplified manner to derive closed form expressions for optimum MSE performance. This has led to the development of non-linear prediction for compensating the split loss (in contrast to the linear prediction using a Gaussian model). We show that the GMM approach can improve the recently proposed adaptive VQ scheme of switched SVQ (SSVQ). We derive the optimum performance expressions for SSVQ, in both variable bit rate and fixed bit rate formats, using the simplified approach of GMM in high rate theory. As a third scheme for recovering the split loss in SVQ and reduce the complexity, we propose a two stage SVQ (TsSVQ), which is analyzed for minimum complexity as well as perceptual distortion. Utilizing the low complexity of transform domain SVQ (TrSVQ) as well as the two stage approach in a universal coding framework, it is shown that we can achieve low complexity as well as better performance than SSVQ. Further, the combination of GMM and universal coding led to the development of a highly scalable coder which can provide both bit-rate scalability, decoder scalability and rate-independent low complexity. Also, the perceptual distortion performance is comparable to that of SSVQ. Since GMM is a generic source model, we develop a new method of predicting the performance bound for perceptual distortion using VQ. Applying this method to LSF quantization, the minimum bit rates for quantizing telephone band LSF (TB-LSF) and wideband LSF (WB-LSF) are derived.

[pt] Esta dissertação propõe algoritmos para codificações de voz a taxas médias em torno de 1,2 Kb/s. Um esquema de quantização vetorial preditiva chaveada com desempenho superior aos esquemas previamente descritos na literatura é proposto e avaliado em canal com ou sem ruído. Detectores eficientes de período fundamental e de sons oclusivos e fricativos são examinados e adaptados ao codificador proposto. Técnicas de exitação a baixas taxas de bits são investigadas a fim de reproduzir uma boa qualidade de voz decodificada. O modelo de exitação mista em multi-bandas com três sub-bandas é adotado para codificar os quadros sonoros. Para os quadros surdos são empregadas técnicas de modelagem e síntese de sinais fricativos e oclusivos, capazes de oferecer qualidade de voz satisfatória, reduzindo a taxa de bits destes quadros para apenas 0,4 Kb/s. Técnicas de pós-filtragem para reduzir o ruído de codificação e melhorar a qualidade de voz reconstruída são também examinadas e comparadas em uma mesma plataforma. Para reduzir o nível de ruído ambiente são ainda analisados métodos de supressão de ruído. Finalmente, o codificador proposto é comparado ao padrão norte-americano Mixed Excitation Linear Prediction (MELP), por meios de teste de comparação do tipo A/B. Os testes realizados indicam que o sistema proposto, operando a 1,2 Kb/s, apresenta qualidade de voz ligeiramente superior ao MELP, operando a 2,4 Kb/s. Para situações de transcodificação, o codificador proposto também apresenta desempenho superior ao MELP. / [en] This dissertation presents algorithms to encode at an avarage bit rate of 1.2 Kb/s. A novel switched-predictive vector quantiser technique that outperforms previously reported schemes is proposed and assessed under noise-free and noisy channels. Efficient detectors for the pitch period and fricative and stop sounds are examined and adapted to the proposed coder. Low bit rate excitation methods are investigated in order to reproduce rather high quality speech. A mixed multiband excitation approach with three sub-bands is employed to encode voiced frames. For unvoiced frames, fricatives and stops modelling and synthesis techniques are used. This approach has shown to provide high quality synthesised speech, whilts it reduces the bit rate to only 0.4 Kb/s for unvoiced frames. To reduce coding noise and improve decoded speech, post- filtering techniques are analysed and compared on the same plataform. To reduce background noise, noise suppression methods are also examined. Finally, the propose coder is evaluated against the North American Mixed Prediction (MELP) coder, through A/B comparison tests. Assessment results have shown that the proposed system, operating at 1.2 Kb/s, slightly outperformed the MELP coder, operating at 2.4 Kb/s. For tandem connection situations, the proposed algorithm has presented a superior performance than the MELP coder. / [es] Esta disertación propone algoritmos para codificaciones de voz a tasas medias en torno de 1,2 Kb/s. Se propone un esquema de cuantización vectorial predictiva, con desempeño superior a los esquemas previamente descritos en la literatura. Este esquema se evalúa en canal con o sin ruido. Se examinan detectores eficientes de período fundamental y de sueños oclusivos y fricativos se adaptan al codificador propuesto. Técnicas de exitación a bajas tasas de bits son investigadas a fin de reproducir una boa calidad de voz decodificada. Se adopta el modelo de exitación mixta en multi-bandas con tres sub-bandas para codificar los cuadros sonoros. Para los cuadros surdos se emplean técnicas de modelación y síntesis de señales fricativos y oclusivos, capaces de ofrecer calidad de voz satisfactoria, reduciendo la tasa de bits de estos cuadros para apenas 0,4 Kb/s. También se examinan y se comparan las técnicas de pós-filtragen para reducir el ruido de codificación y mejorar la calidad de voz reconstruída. Para reducir el nível de ruído ambiente se analizan métodos de supresión de ruido. Finalmente, el codificador propuesto se compara al padrón norteamericano Mixed Excitation Lineal Prediction (MELP), por medio de pruebas de comparación del tipo LA/B. Las pruebas realizadas indican que el sistema propuesto, operando a 1,2 Kb/s, presenta calidad de voz ligeramente superior al MELP, operando a 2,4 Kb/s. Para situaciones de transcodificación, el codificador propuesto también presenta desempeño superior al MELP.

O uso intensivo de áreas do solo provoca alterações na sua qualidade, tornando-se necessária a criação de métodos de avaliação e monitoramento. A técnica de Avaliação do Ciclo de Vida (ACV) é uma importante ferramenta para o cálculo de impactos ambientais, relativos a um sistema de produto com fronteiras delimitadas, sendo o Uso do Solo uma das categorias de impacto avaliada. Na ACV este impacto é avaliado, a partir de fatores de caracterização, os quais utilizam indicadores que quantificam as consequências de modificações na estrutura do solo, levando em consideração a realidade e as características morfológicas de cada país ou região. Este estudo tem como objetivo apresentar adequações relacionadas às condições brasileiras do modelo para a caracterização de impactos provocados pelo uso do solo, a partir da adaptação de fatores de caracterização. De acordo com a pesquisa bibliográfica acerca dos métodos de avaliação do uso do solo na ACV, dois grupos são avaliados a Biodiversidade e as Funções de Suporte de Vida (FSV). Neste estudo foram identificados diferentes métodos que avaliam os impactos nas FSV e a partir de alguns critérios adotados foram posteriormente submetidos a uma análise, a fim de se determinar o método de maior relevância para as condições brasileiras. O método escolhido utiliza como indicador a Matéria Orgânica do Solo (MOS), porém devido à ausência de dados em algumas regiões, podem ser utilizados valores de Carbono Orgânico do Solo (COS), componente essencial da MOS. Os valores para o COS no estado natural foram atribuídos segundo dados de literatura para o bioma Amazônia, os quais foram posteriormente adaptados para se obter o COS para os tipos de uso de solo considerados neste estudo, segundo a realidade brasileira. / The intensive use of land areas cause changes in its quality, making it necessary to create methods for assessing and monitoring. The technique of Life Cycle Assessment (LCA) is an important tool for the calculation of environmental impacts related to a product system with defined borders, and the Land Use category of impact assessed. In this LCA impacts are assessed from factors characterization using indicators that quantify the effects of changes in soil structure, taking into account the reality and the morphological characteristics of each country or region. This study aims to present adjustments related to the Brazilian model for characterizing impacts caused by land use, based on the calculation of characterization factors. In accordance with the literature of the LCA methods, two groups contribute to this category Biodiversity and Life Support Functions (FSV). In this study were discussed and evaluated different methods to calculate (FSV), from some criteria adopted, these were subjected to a comparative analysis, to the method of greatest relevance to Brazilian conditions. The method chosen to use as an indicator of Soil Organic Matter (SOM), but due to lack of data in some regions, can be used values of Soil Organic Carbon (COS) essential component of SOM. The values for COS in the natural state were assigned according to the literature data of the Amazon biome, which were adapted to obtain the COS for the types of land use considered in this study according to the Brazilian reality.

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Anaemia, which is caused by iron deficiency, is a global nutritional disorder of utmost concern. It has been assumed that meat, which contains haem as well as non-haem iron, enhances non-haem iron absorption due to the presence of the “meat factor”. In the experiment reported here, 24 semi-anaemic, 3-week-old piglets were utilised as human nutrition models to assess the effects of dietary lactoferrin, meat and LSF (Low Molecular Weight Sarcoplasmic Fraction) on iron bioavailability during a 4-week feeding period. The parameters that were used as measurements of iron bioavailability were changes in haematological indices, haemoglobin iron repletion efficiency, intestinal morphology and mineral balances. Non-significant (p > 0.05) dietary effects were observed for growth performance and for all the haematological and some histological parameters (small intestine villi height, crypt depth and mucosal thickness). Haemoglobin iron repletion efficiency was highest for the control group and was not significantly different between the other 3 diets. The superiority of the control diet in this respect was not consistent with previous trials and can not be explained. Results suggested that increased retention of calcium, magnesium, phosphorous and manganese tended to inhibit iron absorption. However, the LSF and meat diets significantly (p = 0.003) increased the number of goblet cells/100 µm suggesting that mucin secretion was favoured by these two diets. Additionally, all immunological parameters were significantly (p < 0.05) improved by the LSF diet. As such, the LSF diet can be a potential immunobooster feed ingredient for weanling piglets. Overall, the level of LSF in the LSF diet was insufficient to exert a desirable enhancement of iron bioavailability and betterment of 3 iron status of the semi-anaemic piglets relative to the control group. However, the diet containing LSF was as effective as the meat diet with respect to these characteristics.