Il lavoro di tesi ha come oggetto la valutazione della qualità relazionale dei servizi offerti dal Centro disabilità neuromotorie infantili della Fondazione Ariel e ha come obiettivi l’approfondimento teorico e metodologico dell’approccio relazionale riflessivo alla valutazione, con attenzione alle connessioni tra valutazione e dimensioni organizzative dei servizi alla persona e alla famiglia. Questo approccio multidimensionale e multivision della qualità fa riferimento ad alcune macro-dimensioni organizzative del benessere relazionale generato da un servizio sociale: l’efficienza, l’efficacia, la qualità integrativa, la qualità etica dei fini. Questa prospettiva riflessiva e partecipata di valutazione costituisce un’opportunità per cogliere, descrivere e giudicare il bene comune relazionale generato da un servizio alla persona e alla famiglia in un contesto di bisogni sociali in mutamento, dove strategiche sono personalizzazione e alla familiarizzazione dei servizi. Oltre al potenziale conoscitivo, la valutazione della qualità relazionale dedica particolare attenzione al potenziale trasformativo e morfogenetico della leva valutativa. Metodologicamente l’analisi condotta è stata di tipo quanto-qualitativo. Sono state realizzate interviste semi-strutturate con gli operatori del Centro e una dettagliata analisi della documentazione. Il lavoro partecipato ha condotto alla costruzione di questionario di 35 variabili che è stato esitato da 167 famiglie beneficiarie. Oltre ad un’analisi monovariata dei risultati del questionario sono stati costruiti alcuni indici sintetici su alcune dimensioni critiche della qualità relazionale. / The work relates to evaluation of relational quality of the services offered by Foundation Ariel’s childhood neuromotor disabilities Center . The objectives are the methodological and theoretical study of the relational reflexive evaluation approach, with attention to the connections between evaluation and organizational dimensions services to individuals and families. This multidimensional and multi-vision quality model refers to some macro-organizational dimensions of relational well-being generated by social services: efficiency, effectiveness, quality integration, the quality of ethical purposes. This reflective and participatory evaluation perspective is an opportunity to capture, describe and assess the common good relationship generated by a service to individuals and families, which are strategic to the familiarization and customization in a context of changing social needs. In addition, relational quality evaluation pays particular attention to the transformative and morphogenetic potential of evaluation. Methodologically, the analysis was quanto-qualitative. Semi-structured interviews were conducted with operators of the Centre and a detailed analysis of the documentation was done. The work led to the construction of a questionnaire of 35 variables, which 167 beneficiary families have responded to. Besides monovariata analysis of the results of the questionnaire, some synthetic indexes of some critical dimensions of relational quality were constructed.

Volume 14 of publication series EINGEBETTETE, SELBSTORGANISIERENDE SYSTEME is devoted to the structure oriented evaluation of e-learning. For future knowledge society, beside creation of intelligent technologies, adapted methods of knowledge transfer are required. In this context e-learning becomes a key technology for development of any education system. E-learning is a complex process into which many different groups with specific tasks and roles are included. The dynamics of an e-learning process requires adjusted quality management. For that corresponding evaluation methods are needed. In the present work, Dr.Tudevdagva develops a new evaluation approach for e-learning. The advantage of her method is that in contrast to linear evaluation methods no weight factors are needed and the logical goal structure of an elearning process can be involved into evaluation. Based on general measure theory structure oriented score calculation rules are derived. The so obtained score function satisfies the same calculation rules as they are known from normalised measures. In statistical generalisation, these rules allow the structure oriented calculation of empirical evaluation scores based on checklist data. By these scores the quality can be described by which an e-learning has reached its total goal. Moreover, a consistent evaluation of embedded partial processes of an e-learning becomes possibly. The presented score calculation rules are part of a eight step evaluation model which is illustrated by pilot samples. U. Tudevdagva’s structure oriented evaluation model (SURE model) is by its embedding into the general measure theory quite universal applicable. In similar manner, an evaluation of efficiency of administration or organisation processes becomes possible.

Made available in DSpace on 2014-12-17T14:53:18Z (GMT). No. of bitstreams: 1 SolangeMT_DISSERT.pdf: 1423299 bytes, checksum: 06c560710dc5a0166e9f2bf0e8adbf64 (MD5) Previous issue date: 2013-12-16 / The Expansion Plan of the Federal Network of Vocational Education foresees the construction of 860 new units of instruction until 2020, representing a strong growth against the 140 existing units prior to its disclosure by Federal Government of Brazil, in 2005. The Federal Institutes of Education, Science and Technology have been performing the expansion while experiencing the shortcomings and challenges of units still in development, created in previous phases of the Plan. The quality of the services of these institutions has been evaluated by the control bodies, which require the submission of performance indicators in annual management reports of institutions under their jurisdiction. In this context of expansion process, particularly, is desirable to identify possible changes in quality standards. Thus, this research was motivated by the following problem: there was difference in the performance of the Federal Institutes of Education, Science and Technology after the inauguration of the first units of phase II of the Expansion Plan of the Federal Network of Vocational Education? This is an exploratory-descriptive, ex-post-facto, quantitative approach research, which aims to contribute to the knowledge of the impact of the expansion of the Federal Network. The data were collected from 12 indicators presented in management reports of 38 Federal Institutes through years 2007 to 2011 to evaluate the performances using descriptive statistical techniques. The indicators were analyzed in both consolidated and open manners by the following perspectives: country region, growth of instruction units and institutions origin. Was also performed a multivariate analysis of clusters in order to identify excellence groups of Institutes. The results showed differences in the expansion plan s development among Brazilian regions, both in terms of infrastructure and academic indicators, with better results in the Midwest and South, and that there are differentiated profiles of institutes as its origin, where the best quality indicators occur in those originated by integration of different educational institutions. Still, were identified two excellence groups, with emphasis on academic management, human resources and expansion / O Plano de Expans?o da Rede Federal de Educa??o Profissional prev? a constru??o de 860 novas unidades de ensino at? 2020, representando um intenso crescimento frente ?s 140 unidades existentes antes de sua divulga??o pelo Governo Federal, em 2005. Os Institutos Federais de Educa??o, Ci?ncia e Tecnologia v?m realizando a expans?o enquanto vivenciam as defici?ncias e os desafios das unidades ainda em desenvolvimento, criadas nas fases anteriores do Plano. A qualidade dos servi?os dessas institui??es tem sido avaliada pelos ?rg?os de controle, que requerem a apresenta??o de indicadores de desempenho nos seus Relat?rios de Gest?o anuais. No contexto da expans?o dos Institutos, em particular, deseja-se identificar poss?veis mudan?as os padr?es de qualidade. Assim, esta pesquisa foi motivada pelo seguinte problema: houve diferen?a no desempenho dos Institutos Federais de Educa??o, Ci?ncia e Tecnologia ap?s a inaugura??o das primeiras unidades da Fase II do Plano de Expans?o da Rede Federal de Educa??o Profissional e Tecnol?gica? Trata-se de uma pesquisa explorat?rio-descritiva ex-post-facto com abordagem quantitativa, que objetiva contribuir para o conhecimento do impacto da Expans?o da Rede Federal. Foram coletados os dados dos 12 indicadores apresentados nos Relat?rios de Gest?o dos 38 Institutos Federais nos anos 2007 a 2011, para avalia??o dos desempenhos atrav?s de t?cnicas de estat?stica descritiva. Os indicadores foram analisados de forma consolidada e aberta pelas seguintes perspectivas: por regi?o do pa?s, por crescimento de unidades de ensino e por origem das institui??es. Tamb?m foi realizada uma an?lise multivariada de clusters no intuito de identificar grupos de excel?ncia dentre os Institutos. Os resultados evidenciaram haver diferen?as no desenvolvimento do Plano de Expans?o entre as regi?es brasileiras, tanto no plano da infraestrutura quanto nos indicadores acad?micos, com melhores resultados no Centro-Oeste e Sul, e que h? perfis diferenciados de Institutos conforme sua origem, onde os melhores indicadores de qualidade ocorrem naqueles originados por integra??o de diferentes institui??es de ensino. Ainda, foram identificados dois grupos de excel?ncia, com ?nfase em gest?o acad?mica, de pessoas e de expans?o

La segmentation est une tâche cruciale en analyse d’images. L’évolution des capteurs d’acquisition induit de nouvelles images de résolution élevée, contenant des objets hétérogènes. Il est aussi devenu courant d’obtenir des images d’une même scène à partir de plusieurs sources. Ceci rend difficile l’utilisation des méthodes de segmentation classiques. Les approches de segmentation hiérarchiques fournissent des solutions potentielles à ce problème. Ainsi, l’Arbre Binaire de Partitions (BPT) est une structure de données représentant le contenu d’une image à différentes échelles. Sa construction est généralement mono-critère (i.e. une image, une métrique) et fusionne progressivement des régions connexes similaires. Cependant, la métrique doit être définie a priori par l’utilisateur, et la gestion de plusieurs images se fait en regroupant de multiples informations issues de plusieurs bandes spectrales dans une seule métrique. Notre première contribution est une approche pour la construction multicritère d’un BPT. Elle établit un consensus entre plusieurs métriques, permettant d’obtenir un espace de segmentation hiérarchique unifiée. Par ailleurs, peu de travaux se sont intéressés à l’évaluation de ces structures hiérarchiques. Notre seconde contribution est une approche évaluant la qualité des BPTs en se basant sur l’analyse intrinsèque et extrinsèque, suivant des exemples issus de vérités-terrains. Nous discutons de l’utilité de cette approche pour l’évaluation d’un BPT donné mais aussi de la détermination de la combinaison de paramètres adéquats pour une application précise. Des expérimentations sur des images satellitaires mettent en évidence la pertinence de ces approches en segmentation d’images. / Segmentation is a crucial task in image analysis. Novel acquisition devices bring new images with higher resolutions, containing more heterogeneous objects. It becomes also easier to get many images of an area from different sources. This phenomenon is encountered in many domains (e.g. remote sensing, medical imaging) making difficult the use of classical image segmentation methods. Hierarchical segmentation approaches provide solutions to such issues. Particularly, the Binary Partition Tree (BPT) is a hierarchical data-structure modeling an image content at different scales. It is built in a mono-feature way (i.e. one image, one metric) by merging progressively similar connected regions. However, the metric has to be carefully thought by the user and the handling of several images is generally dealt with by gathering multiple information provided by various spectral bands into a single metric. Our first contribution is a generalized framework for the BPT construction in a multi-feature way. It relies on a strategy setting up a consensus between many metrics, allowing us to obtain a unified hierarchical segmentation space. Surprisingly, few works were devoted to the evaluation of hierarchical structures. Our second contribution is a framework for evaluating the quality of BPTs relying both on intrinsic and extrinsic quality analysis based on ground-truth examples. We also discuss about the use of this evaluation framework both for evaluating the quality of a given BPT and for determining which BPT should be built for a given application. Experiments using satellite images emphasize the relevance of the proposed frameworks in the context of image segmentation.

Les modèles conceptuels (MC) jouent un rôle crucial qui est celui de servir de base à l’ensemble du processus de développement d’un système d’information (SI) mais aussi de moyen de communication à la fois au sein de l’équipe de développement et avec les utilisateurs durant les premières étapes de validation. Leur qualité joue par conséquent un rôle déterminant dans le succès du système final. Des études ont montré que la majeure partie des changements que subit un SI concerne des manques ou des défaillances liés aux fonctionnalités attendues. Sachant que la définition de ses fonctionnalités incombe à la phase de l’analyse et conception dont les MC constituent les livrables, il apparaît indispensable pour une méthode de conception de veiller à la qualité des MC qu’elle produit. Notre approche vise les problèmes liés à la qualité de la modélisation conceptuelle en proposant une solution intégrée au processus de développement qui à l’avantage d’être complète puisqu’elle adresse à la fois la mesure de la qualité ainsi que son amélioration. La proposition couvre les aspects suivants: i. Formulation de critères de qualité en fédérant dans un premier temps les travaux existant sur la qualité des MC. En effet, un des manques constaté dans le domaine de la qualité des MC est l’absence de consensus sur les concepts et leurs définitions. Ce travail a été validé par une étude empirique. Ce travail a également permis d’identifier les parties non couverte par la littérature et de les compléter en proposant de nouveaux concepts ou en précisant ceux dont la définition n’était complète. ii. Définition d’un concept (pattern de qualité) permettant de capitaliser les bonnes pratiques dans le domaine de la mesure et de l’amélioration de la qualité des MC. Un pattern de qualité sert à aider un concepteur de SI dans l’identification des critères de qualité applicables à sa spécification, puis de le guider progressivement dans la mesure de la qualité ainsi que dans son amélioration. Sachant que la plupart des approches existantes s’intéresse à la mesure de la qualité et néglige les moyens de la corriger. La définition de ce concept est motivée par la difficulté et le degré d’expertise important qu’exige la gestion de la qualité surtout au niveau conceptuel où le logiciel fini n’est pas encore disponible et face à la diversité des concepts de qualité (critères et métriques) pouvant s’appliquer. iii. Formulation d’une méthode orientée qualité incluant à la fois des concepts, des guides et des techniques permettant de définir les concepts de qualité souhaités, leur mesure et l’amélioration de la qualité des MC. Cette méthode propose comme point d’entrée le besoin de qualité que doit formuler le concepteur. Il est ensuite guidée de manière flexible dans le choix des critères de qualité adaptés jusqu’à la mesure et la proposition de recommandations aidant à l’amélioration de la qualité du MC initial conformément au besoin formulé. iv. Développement d'un prototype "CM-Quality". Notre prototype met en œuvre la méthode proposée et offre ainsi une aide outillé à son application. Nous avons enfin mené deux expérimentations ; la première avait comme objectif de valider les concepts de qualité utilisés et de les retenir. La deuxième visait à valider la méthode de conception guidée par la qualité proposée / Conceptual models (CM) serve as the blueprints of information systems and their quality plays decisive role in the success of the end system. It has been witnessed that majority of the IS change-requests result due to deficient functionalities in the information systems. Therefore, a good analysis and design method should ensure that CM are correct and complete, as they are the communicating mediator between the users and the development team. Our approach targets the problems related to conceptual modeling quality by proposing a comprehensive solution. We designed multiple artifacts for different aspects of CM quality. These artifacts include the following: i. Formulation of comprehensive quality criteria (quality attributes, metrics, etc.) by federating the existing quality frameworks and identifying the quality criteria for gray areas. Most of the existing literature on CM quality evaluation represents disparate and autonomous quality frameworks proposing non-converging solutions. Thus, we synthesized (existing concepts proposed by researchers) and added the new concepts to formulate a comprehensive quality approach for conceptual models that also resulted in federating the existing quality frameworks. ii. Formulation of quality patterns to encapsulate past-experiences and good practices as the selection of relevant quality criteria (including quality attributes and metrics) with respect to a particular requirement (or goal) remains trickier for a non-expert user. These quality patterns encapsulate valuable knowledge in the form of established and better solutions to resolve quality problems in CM. iii. Designing of the guided quality driven process encompassing methods and techniques to evaluate and improve the conceptual models with respect to a specific user requirement or goal. Our process guides the user in formulating the desired quality goal, helps him/her in identifying the relevant quality patterns or quality attributes with respect to the quality goal and finally the process helps in evaluating the quality of the model and propose relevant recommendations for improvement. iv. Development of a software prototype “CM-Quality”. Our prototype implements all the above mentioned artifacts and proposes a workflow enabling its users to evaluate and improve CMs efficiently and effectively. We conducted a survey to validate the selection of the quality attributes through the above mentioned federating activity and also conducted three step detailed experiment to evaluate the efficacy and efficiency of our overall approach and proposed artifacts.

Volume 14 of publication series EINGEBETTETE, SELBSTORGANISIERENDE SYSTEME is devoted to the structure oriented evaluation of e-learning. For future knowledge society, beside creation of intelligent technologies, adapted methods of knowledge transfer are required. In this context e-learning becomes a key technology for development of any education system. E-learning is a complex process into which many different groups with specific tasks and roles are included. The dynamics of an e-learning process requires adjusted quality management. For that corresponding evaluation methods are needed. In the present work, Dr.Tudevdagva develops a new evaluation approach for e-learning. The advantage of her method is that in contrast to linear evaluation methods no weight factors are needed and the logical goal structure of an elearning process can be involved into evaluation. Based on general measure theory structure oriented score calculation rules are derived. The so obtained score function satisfies the same calculation rules as they are known from normalised measures. In statistical generalisation, these rules allow the structure oriented calculation of empirical evaluation scores based on checklist data. By these scores the quality can be described by which an e-learning has reached its total goal. Moreover, a consistent evaluation of embedded partial processes of an e-learning becomes possibly. The presented score calculation rules are part of a eight step evaluation model which is illustrated by pilot samples. U. Tudevdagva’s structure oriented evaluation model (SURE model) is by its embedding into the general measure theory quite universal applicable. In similar manner, an evaluation of efficiency of administration or organisation processes becomes possible.

The use of Virtual Reality (VR) is growing in commercial use, one type of VR headset, called mobile stand-alone system has limited resources for computing and memory. Because of this, when developing real-time applications for this type of VR headset, performance needs to be heavily considered. One popular optimization technique is Level-of-Detail (LOD) which is a technique that represents a model at various resolutions. One type of LOD is called continuous LOD which can represent a model at a continuous spectrum of detail, this is not frequently used, however, because of being less intuitive and more difficult to implement than other versions. This project researched a type of continuous LOD used with a new metric called Pixel Quality Per Meter (PQPM). PQPM relies on having a minimum edge length calculated using a model's screen coverage in relation to its size. To answer whether PQPM can be used together with continuous LOD for intuitive, simple, and efficient updating and rendering in VR. The continuous LOD only uses one low-poly mesh which is tessellated with the help of a Vertex Displacement Map (VDM) to the desired quality. This approach is then evaluated using Nvidia FLIP, an image comparison application that emulates the human visual system. The result was an intuitive and easily implementable LOD which is used together with PQPM to decide the optimal quality given the models size and coverage on the screen. The usage of PQPM did not result in optimal quality at all distances, due to smaller segments being present, which could disappear completely at far distances. The continuous LOD combined with the PQPM did also not scale well but worked well at lower qualities. The study showed groundwork for how PQPM could work together with continuous LOD, it provides a more intuitive and easily implementable continuous LOD than previous approaches, however, because of the scalability issues, further work needs to be done to optimize this approach. / Användingen av Virtual Reality (VR) i kommersiellt syfte ökar, en typ av dessa VR headsets kallas mobila fristående system. Mobila fristående system har begränsade resurser när det kommer till att göra beräkningar och minne. På grund av detta måste man noga överväga prestanda. En populär optimeringsmetod kallas Level-of-Detail (LOD) vilket är en metod som kan representera en modell på ett antal olika upplösningar. En typ av LOD kallas kontinuerlig LOD som kan representera en modell med en kontinuerling detaljnivå. Denna används inte frekvent däremot på grund av att den är mindre intuitiv och svårare att implementera och uppdatera detaljnivå. Detta projektet undersökte en typ av kontinuerlig LOD där den används tillsammans med ett nytt metriskt mått som kallas Pixel Quality Per Meter (PQPM). PQPM byggs på att beräkna en minimal kantlängd via hur stor del av skärmen den täcker i relation till dess storlek. Detta undersöks för att besvara ifall PQPM kan användas tillsammans med kontinuerlig LOD för intuitiv, simpel och effektiv uppdatering och rendering i VR. Den kontinuerliga LOD använder sig bara av en low-poly mesh som är tessellerad med hjälp av en Vertex Displacement Map (VDM) till en önskad kvalitet. Detta evalueras sedan genom Nvidia FLIP, en bildjämförelseapplikation som emulerar människosyn. Resultatet var en intuitiv och enkelt implementerbar kontinuerlig LOD som användes tillsammans med PQPM för att bestämma den optimala detaljnivån baserat på modellens storlek och hur mycket av skärmen den täckte. Användingen av PQPM resulterade inte i optimal kvalitet för alla distanser, på grund av mindre segment som kunde försvinna helt på längre distanser. Den kontinuerliga LOD tillsammans med PQPM hade dålig skalning i prestanda men fungerade bra vid lägre kvalitetsnivåer. Studien visa grundarbetet för hur PQPM kan användas tillsammans med kontinuerlig LOD. Detta tillvägagångsättet tillät för ett mer intuitivt och simpelt sätt att implementera än tidigare tillvägagångssätt. Däremot, på grund av skalningsproblemen, fortsatt arbete måste göras för att optimera detta tillvägagångssättet.

Cycling is recognised as a mode of transport with many health and environmental benefits yet remains relatively underfunded and lacks priority in many Swedish municipalities. Despite a will from the government to enhance sustainable transport, cycling is not given its rightful place in urban areas. This implies a presence of bottlenecks and barriers in cycle planning. Cycle advocacy organisations try to change this paradigm and develop tools, methods, and processes to improve this process. Cycling advocacy Cykelfrämjandet recently released a new process called Cyklisternas Cykelvägsanalys, cyclists’ cycle route analysis. This process can be used by any usual cyclist who will invite decision makers to experience the cycling environment and evaluate it together using a quality assessment method. A report is handed over to the municipality afterwards and a follow up is done one year after.To fully grasp what this new process entails, a thorough document analysis was conducted. Through an international review exploring similar initiatives developed by NGOs, individuals or governmental entities, the degree of innovation this process was assessed. This was then built upon using semi constructed interviews with participants of the three trial Cykelvägsanalys happening in Marks Kommun, Pitea and Varberg. The interview results were also used to evaluate how Cyklisternas Cykelvägsanalys can work on bottlenecks and use action levers to improve the cycling environment. Results show that whilst other methods to assess the quality of cycling environmentsexist, none are tied into a process, or at least nothing of the official kind. This emphasis on the process, the communication that it creates between politicians, planners, and everyday cyclists can help lift bottlenecks related to cycle planning linked to a lack of political support and the weak cycle lobby. In the three municipalities, it seems that CVA has more impact on municipalities that are less advanced on the cycling question. The results are very promising, and the participants on the municipal side willing to act on recommendations issued from the workshop. A big drawback however is the presence of very few politicians in the workshops which is what would have the most impact. A bigger emphasis on the necessity of getting these actors to participate in the methodology would be beneficial. More research can be done in a few years to assess the impact of follow up and if everyday cyclists took the initiative of trying out the method in their municipalities.

Les travaux de recherche présentés dans ce manuscrit décrivent plusieurs apports au thème de l’évaluation de la qualité d’images de documents numérisés. Pour cela nous proposons de nouveaux descripteurs permettant de quantifier les dégradations les plus couramment rencontrées sur les images de documents numérisés. Nous proposons également une méthodologie s’appuyant sur le calcul de ces descripteurs et permettant de prédire les performances d’algorithmes de traitement et d’analyse d’images de documents. Les descripteurs sont définis en analysant l’influence des dégradations sur les performances de différents algorithmes, puis utilisés pour créer des modèles de prédiction à l’aide de régresseurs statistiques. La pertinence, des descripteurs proposés et de la méthodologie de prédiction, est validée de plusieurs façons. Premièrement, par la prédiction des performances de onze algorithmes de binarisation. Deuxièmement par la création d’un processus automatique de sélection de l’algorithme de binarisation le plus performant pour chaque image. Puis pour finir, par la prédiction des performances de deux OCRs en fonction de l’importance du défaut de transparence (diffusion de l’encre du recto sur le verso d’un document). Ce travail sur la prédiction des performances d’algorithmes est aussi l’occasion d’aborder les problèmes scientifiques liés à la création de vérités-terrains et d’évaluation de performances. / This PhD. thesis deals with quality evaluation of digitized document images. In order to measure the quality of a document image, we propose to create new features dedicated to the characterization of most commons degradations. We also propose to use these features to create prediction models able to predict the performances of different types of document analysis algorithms. The features are defined by analyzing the impact of a specific degradation on the results of an algorithm and then used to create statistical regressors.The relevance of the proposed features and predictions models, is analyzed in several experimentations. The first one aims to predict the performance of different binarization methods. The second experiment aims to create an automatic procedure able to select the best binarization method for each image. At last, the third experiment aims to create a prediction model for two commonly used OCRs. This work on performance prediction algorithms is also an opportunity to discuss the scientific problems of creating ground-truth for performance evaluation.

[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.