This study is about replacing an old bluetooth module with a new variant, namely the BM83 which is an integrated circuit that contains an internal DSP circuit, profiles and important functions such as noise reduction, acoustic echo removal and EQ filtering. The purpose of this study is to replace the old module with the BM83, as well as explore the internal DSP circuit in the BM83. The goal is to develop the audio system with a high performance bluetooth and explore the BM83's built-in DSP functions and its profiles to optimize sound quality. This study takes different methods and performs different experiments to test the ability of BM83 to replace RN52 in a DSP platform. In addition, it was proposed that an audiosystem should be managed in an operating system with the idea of optimizing data transfer by using some of new operating system mechanism methods. In this study, the differences between BM83 and RN52 were discussed in terms of their profiles, built-in CODEC and DSP algorithm.This study provides how SPP, A2DP and HFP can be used together when the BM83 is controlled by a DSP platform. In addition, it was tested how A2DP and HFP have a great importance in providing events that a DSP platform can decide on and how it chooses its source depending on these events. In addition, the data communication between the BM83 and an STM32F7 was tested via the SPP protocol, with the idea that any data would be sent and received via SPP without loss in data transmission. In conclusion, it was discussed what type of data communication is used between BM83 and an MCU in comparison between RN52 and how the built-in DSP circuit and itsprofiles are important for future research. This project was funded by the Hearing Research Foundation in project FA21-0017 and was carried out under the supervision of Amin Saremi. / Denna studie handlar om att ersätta en gammal bluetooth modul med en ny variant, nämligen BM83 som är en integrerad krets som innehåller en interna DSP krets, profiler och viktiga funktioner som brusreducering, akustisk ekoborttagning och EQ-filtrering. Syftet med denna studie är att ersätta den gamla modulen med BM83, samt utforska den interna DSP kretsen i BM83. Målet är att utveckla ljudsystemet med en högprestanda bluetooth och utforska BM83:s inbyggda DSP-funktioner och dess profilerför att optimera ljudkvalitet. Denna studie tar olika metoder och utför olika experiment för att testa BM83:s förmåga att ersätta RN52 i en DSP plattform. Dessutom föreslogs om att hur ett ljudsystem skulle hanteras i ett operativsystem med tanken på att optimera dataöverföringen. I denna studie diskuterades skillnaderna mellan BM83 och RN52 när det gäller deras profiler, inbyggda CODEC- och DSP-algoritmen. I denna studie belystes hur SPP, A2DP och HFP användes tillsammans när BM83 styrdes av en DSP plattform. Dessutom testades hur A2DP och HFP har en stor betydelse för att tillhandahålla händelser som kan en DSP plattform bestämma sig av och hur den väljer sin källa beroende på dessa händelser. Dessutom testades datakommunikationen mellan BM83 och en STM32F7 via SPP protokollet, med tanken på att valfri data skulle skickas och tas emot via SPP utan förlust i dataöverföring. Avslutningsvis diskuterades vilken typ av datakommunikation används mellan BM83 ochen MCU i jämförelse mellan RN52 och hur den inbyggda DSP kretsen och dess profiler är viktiga för framtida forskningar. Detta projekt finansierades av Hörselforskningsfonden i projekt FA21-0017 och utfördes under uppsikt av Amin Saremi.

Response time is one of the most important performance measures associated with a typical multi-user system. Response time, in turn, is bounded by the performance of the input/output (I/O) subsystem. Other than the end user and some external peripherals, the slowest component of the I/O subsystem is the disk drive. One standard strategy for improving I/O subsystem performance uses high-performance hardware like Small Computer Systems Interface (SCSI) drives to improve overall response time. SCSI hardware, unfortunately, is often too expensive to use in low-end multi-user systems. The low-end multi-user systems commonly use inexpensive Integrated Drive Electronics (IDE) disk drives to keep overall costs low. On such IDE based multi-user systems, reducing the Central Processing Unit (CPU) overhead associated with disk I/O is critical to system responsiveness. This thesis explores the impact of PCI bus mastering Direct Memory Access (DMA) on the performance of systems with IDE drives. DMA is a data transfer protocol that allows data to be sent directly from an attached device to a computer system’s main memory, thereby reducing CPU overhead. PCI bus mastering allows modern IDE disk controllers to manipulate main memory without utilizing motherboard-resident DMA controllers. Using a series of experiments, this thesis examines the impact of PCI bus mastering DMA on IDE performance for synchronous I/O, relative to Programmed Input/Output (PIO) and SCSI performance. Experiment results show that PCI bus mastering DMA, when used properly, improves the responsiveness and throughput of IDE drives by as much as a factor of seven. The magnitude of this improvement shows the importance of operating system support for DMA in low-end multi-user systems. Additionally, experimental results demonstrate that performance gains associated with SCSI are dependent on system usage and operating system support for advanced SCSI capabilities. Therefore, under many circumstances, high-performance SCSI drives are not cost effective when compared with IDE bus mastering DMA capable drives.

The research reported in this dissertation focuses on the development of optimization tools for the design of subsystems in a modern aircraft power distribution system. The baseline power distribution system is built around a 270V DC bus. One of the distinguishing features of this power distribution system is the presence of regenerative power from the electrically driven flight control actuators and structurally integrated smart actuators back to the DC bus. The key electrical components of the power distribution system are bidirectional switching power converters, which convert, control and condition electrical power between the sources and the loads. The dissertation is divided into three parts. Part I deals with the formulation of an optimization problem for a sample system consisting of a regulated DC-DC buck converter preceded by an input filter. The individual subsystems are optimized first followed by the integrated optimization of the sample system. It is shown that the integrated optimization provides better results than that obtained by integrating the individually optimized systems. Part II presents a detailed study of piezoelectric actuators. This study includes modeling, optimization of the drive amplifier and the development of a current control law for piezoelectric actuators coupled to a simple mechanical structure. Linear and nonlinear methods to study subsystem interaction and stability are studied in Part III. A multivariable impedance ratio criterion applicable to three phase systems is proposed. Bifurcation methods are used to obtain global stability characteristics of interconnected systems. The application of a nonlinear design methodology, widely used in power systems, to incrementally improve the robustness of a system to Hopf bifurcation instability is discussed. / Ph. D.

Um eine zielgerichtete Ableitung von Fahrzeugeigenschaften in frühen Entwicklungsphasen zu ermöglichen, ist eine Subsystemebene erforderlich, die eine konzeptunabhängige Auslegung des Gesamtfahrzeugverhaltens zulässt. In der vorliegenden Arbeit wird daher eine neue Methodik zur Auslegung von Fahrkomfort-Kennwerten auf Basis von Subsystemeigenschaften vorgestellt. Neben der Entwicklung eines geeigneten Modellansatzes, in dem die Subsysteme des Gesamtfahrzeugs durch Greybox-Modelle ohne Komponentenbezug miteinander verknüpft werden, stehen dabei auch dessen Parametrierung sowie die Integration der Methodik im Entwicklungsprozess im Vordergrund. Zur Ableitung der damit verbundenen physikalisch-mechanischen Zusammenhänge werden statische und dynamische Achsprüfstände sowie Simulationen eingesetzt. Die Anwendung der Methodik lässt eine gezielte Eigenschaftsableitung zwischen Gesamtfahrzeug-, Subsystem- und Komponentenebene im Fahrkomfort zu, bei der die Subsystemebene als neue Referenz für die Ableitung von Komponenteneigenschaften dient. Weiterhin erlaubt das Vorgehen eine eigenschaftsbasierte Vorauswahl optimaler Komponentenkonzepte sowie detaillierte Wettbewerbsanalysen. Dadurch wird eine nachhaltige Steigerung der Effizienz im Entwicklungsprozess des Fahrkomforts ermöglicht.

Ubiquitous Sensor Network (USN) est un réseau conceptuel construit sur des réseaux physiques existantes. Il se sert des données détectées et fournit des services de connaissances à quiconque, n'importe où et à tout moment, et où l'information est générée en utilisant la sensibilité au contexte. Dispositifs et USN portables intelligents émergent rapidement en offrant de nombreux services fiables facilitant la vie des gens. Ces petits terminaux et terminaux très utiles besoin d'un substrat de communication globale pour fournir un service complet de l'utilisateur final global. En 2010, ITU -T a fourni les exigences pour supporter des applications et services USN dans le Next Generation Network (NGN) de l'environnement d'exploiter les avantages du réseau de base. L'un des principaux marchés prometteurs pour l'application et les services USN est la e- santé. Il fournit le suivi des patients en continu et permet une grande amélioration dans les services médicaux. D'autre part, des Véhicules Ad-hoc NETwork (VANET) est une technologie émergente qui permet une communication intelligente entre les véhicules mobiles. Intégrer VANET avec USN a un grand potentiel pour améliorer la sécurité routière et la fluidité du trafic. La plupart des applications VANET sont appliqués en temps réel et ils sont sensibles à retarder, en particulier ceux liés à la sécurité et à la santé. Dans ce travail, nous proposons d'utiliser l'IP Multimédia Subsystem (IMS) comme une sous- couche de contrôle de service dans l'environnement USN fournir un substrat mondiale pour un service complet de bout en bout. De plus, nous vous proposons d'intégrer VANETs avec USN pour des applications et des installations riches plus, ce qui facilitera la vie des humains. Nous avons commencé à étudier les défis sur la route pour atteindre cet objectif / Ubiquités Sensor Network (USN) is a conceptual network built over existing physical networks. It makes use of sensed data and provides knowledge services to anyone, anywhere and at anytime, and where the information is generated by using context awareness. Smart wearable devices and USNs are emerging rapidly providing many reliable services facilitating people life. Those very useful small end terminals and devices require a global communication substrate to provide a comprehensive global end user service. In 2010, the ITU-T provided the requirements to support USN applications and services in the Next Génération Network (NGN) environment to exploit the advantages of the core network. One of the main promising markets for the USN application and services is the e-Health. It provides continuous patients’ monitoring and enables a great improvement in medical services. On the other hand, Vehicular Ad-Hoc NETwork (VANET) is an emerging technology, which provides intelligent communication between mobile vehicles. Integrating VANET with USN has a great potential to improve road safety and traffic efficiency. Most VANET applications are applied in real time and they are sensitive to delay, especially those related to safety and health. In this work, we propose to use IP Multimedia Subsystem (IMS) as a service controller sub-layer in the USN environment providing a global substrate for a comprehensive end-to-end service. Moreover, we propose to integrate VANETs with USN for more rich applications and facilities, which will ease the life of humans. We started studying the challenges on the road to achieve this goal

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / For many years VME has been the platform of choice for high-performance, real-time data acquisition systems. VME’s longevity has been made possible in part by timely enhancements which have expanded system bandwidth and allowed systems to support ever increasing throughput. One of the most recent ANSI-standard extensions of the VME specification defines RACEway, a system of dynamically switched, 160 Mbyte/second board-to-board interconnects. In typical systems RACEway increases the internal bandwidth of a VME system by an order of magnitude. Since this bandwidth is both scaleable and deterministic, it is particularly well suited to high-performance, real-time systems. The potential of RACEway for very high-performance (200 Mbps to 1 Gbps) real-time systems has been recognized by both the VME industry and a growing number of system integrators. This recognition has yielded many new RACEway-ready VME products from more than a dozen vendors. In fact many significant real-time data acquisition systems that consist entirely of commercial-off-the-shelf (COTS) RACEway products are being developed and fielded today. This paper provides an overview of RACEway technology, identifies the types of RACEway equipment currently available, discusses how RACEway can be applied in high-performance data acquisition systems, and briefly describes two systems that acquiring and capturing real-time data streams at rates from 200 Mbps to 1 Gbps using RACEway.

Os povos indígenas vivem há mais de 500 anos na luta pela superação do colonialismo interno. Com a homogeneização das formas de vida, estes povos são sistematicamente produzidos como não existentes nas políticas integracionistas. A Constituição Federal de 1988 rompe com esta prática garantindo o direito do reconhecimento de suas identidades e modos de vida, expressos pela sua cultura, e o direito à saúde. O direito dos povos originários à saúde pautou três Conferências de Saúde Indígena que estabeleceram as diretrizes para a criação do Subsistema de Atenção à Saúde Indígena em 1999. Desde o início de sua estruturação nos 34 Distritos Sanitários Especiais Indígenas (DSEI), foram organizados os Conselhos Distritais de Saúde Indígena (CONDISI) e o Fórum de Presidentes de CONDISI no nível central. Este estudo tem como objetivo analisar a participação e o protagonismo dos povos indígenas no processo de construção e implementação da Política Nacional de Saúde Indígena, após a Constituição Federal de 1988, a partir das Epistemologias do Sul. Foi utilizada a metodologia qualitativa com diversas fontes e materiais: análise documental das atas de reuniões, legislações, relatórios das cinco Conferências Nacionais de Saúde Indígena e 24 entrevistas em profundidade com indígenas, gestores, indigenistas e representante do MPF. A análise das legislações reconhecidas como pertinentes ao tema indicam uma grande quantidade e diversidade de normas que tratam de forma segregada as temáticas indígenas e as normas do Sistema Único de Saúde. Demonstram, para além da fragmentação legal e normativa, algumas iniciativas que avançam na integralidade da assistência, bastante pontuais, como a criação de incentivos financeiros específicos. Destaca-se a complexidade e a fragilidade da articulação interfederativa, que se torna mais complexa com a gestão federal e a territorialização dos DSEI, que não coincidem com os territórios de estados e municípios. No que tange à participação, pode-se afirmar que a maioria dos entrevistados reconhecem o CONDISI como espaço legítimo de diálogo entre indígenas e governo para debater a política de saúde e sua execução nas aldeias indígenas. Contudo, é evidente o predomínio das pautas de interesse da gestão e a repercussão nas reuniões de CONDISI de temas já discutidos no Fórum de Presidentes. Nas pautas do CONDISI Litoral Sul, que foram objeto deste estudo, por exemplo, a discussão da divisão territorial do DSEI, de interesse dos indígenas, não ganhou espaço e reconhecimento pela gestão. Chama a atenção à ausência de discussão nos espaços formais de temas que predominam nas entrevistas com os indígenas, como a valorização da medicina tradicional e a atenção diferenciada. Esta última é a justificativa central para existência do Subsistema e pauta-se nas desigualdades em saúde, na necessidade de modos de produção de cuidado que articulem as medicinas indígenas e a biomedicina e na diversidade cultural dos mais de 300 povos. O predomínio da biomedicina como forma científica e legítima do saber sobre a saúde acaba por interditar as pautas referentes às medicinas indígenas. Esta lógica perpetua a relação colonial do governo com os povos originários, principalmente sobre o saber, comprometendo a efetivação da atenção diferenciada, e, por consequência, do direito à saúde. Esta política, para ser efetiva, deveria se organizar na perspectiva da Ecologia de Saberes, considerando os modos de existência destes povos, principalmente sua relação com a terra, e sua construção como sujeitos coletivos. / Indigenous Peoples have been living for more than 500 years in the struggle to overcome internal colonialism. With the homogenization of the way of life, these peoples are systematically considered as non-existent in integrationist policies. The Federal Constitution of 1988 breaks with this logic assuring them the right to their identities and their ways of life, expressed by their culture, and also their right to health. The Indigenous Peoples\' right to health established three Indigenous Health Conferences that set the guidelines for the creation of the Indigenous Health Care Subsystem, in 1999. Since its beginning, along with the establishiment of the 34 Special Indigenous Sanitary Districts (DSEI), participatory Councils were organized (CONDISI), and also the CONDISI Presidents\' Forum at the central level. Based on Epistemologies of the South, this study aims to analyze the participation and the protagonism of Indigenous Peoples in the construction and implementation processes of the National Indigenous Health Policy, after the Federal Constitution of 1988. The qualitative methodology used with several sources and materials: documenta analysis of minutes of meetings, legislations, reports of the five National Indigenous Health Conferences and 24 in-depth interviews with Indigenous Peoples, managers, indigenists and Federal Prosecution Service. Relevant legislation analyzed showed great quantity and diversity of norms that separate the indigenous themes and the norms of the Unified Health System. They demonstrate, in addition to legal and normative fragmentation, some initiatives towards care integrality quite specific ones, such as the creation of financial incentives. We highlight the complexity and fragility of the interfederative articulation, which becomes more complex with federal management and territorialisation of the DSEI, which do not match with the limits of states and municipalities territories. Regarding participation, it can be said that most interviewees recognize the CONDISI as a legitimate space for dialogue between Indigenous Peoples and the government to discuss the health policy and its implementation in indigenous communities. However, there is a clear predominance of agendas in the interest of the management representatives and the repercussions on the CONDISI meetings of topics already discussed in the Presidents\' Forum. For example, on the agenda of the CONDISI Litoral Sul, object of this study, the discussion of the territorial division of the DSEI, on the interest of the indigenous representatives, did not gain space and recognition by the management representatives. What also draws attention is the absence of discussions of topics that were predominant on the interviews with Indigenous Peoples on formal spaces, such as traditional medicine and differentiated care. This last one is central to the existence of the Subsystem and it is based on inequalities in health, the need for care production methods that articulate traditional indigenous medicine and biomedicine, and the cultural diversity of more than 300 tribes. The predominance of biomedicine as a scientific and legitimate way of health knowledge inhibits the agenda related to traditional indigenous medicine. This logic perpetuates the colonial relationship of the government upon the Indigenous Peoples, especially regarding knowledge, compromising the effectiveness of differentiated care and, consequently, the right to health. This policy, in order to be effective, should be organized in the perspective of the Ecology of Knowledges, considering the ways of existence of these peoples, especially their relationship with the land, and their construction as collective subjects.

Submitted by JOSIANE SANTOS DE OLIVEIRA (josianeso) on 2017-07-10T13:21:23Z No. of bitstreams: 1 Nicolau Cardoso Neto_.pdf: 4708309 bytes, checksum: 1dd8c22aad711af3486a701ea6beea21 (MD5) / Made available in DSpace on 2017-07-10T13:21:23Z (GMT). No. of bitstreams: 1 Nicolau Cardoso Neto_.pdf: 4708309 bytes, checksum: 1dd8c22aad711af3486a701ea6beea21 (MD5) Previous issue date: 2016-12-13 / Nenhuma / A presente Tese apresenta uma abordagem acerca da identificação da ocorrência de acoplamento estrutural entre as operações dos Subsistemas Jurídico Ambiental e Jurídico de Saúde do Sistema Jurídico Brasileiro. Para tanto, utilizou-se a água com qualidade e potável para o consumo humano como operação para compreender se ocorrem irritações entre as estruturas dos referidos subsistemas. Emprega-se como teoria de base os Sistemas Sociais de Niklas Luhmann, em especial O Direito da Sociedade, para a realização de autodescrição dos subsistemas para então aplicar a comparação e a identificação das irritações entre as estruturas que provocam o acoplamento estrutural. É empregado o método de abordagem Sistêmico, com a intenção de realizar comparação entre os subsistemas por meio da realização de autorreferência de vinte e quatro normas. Também foram empregados os métodos de Procedimento Comparativo e Funcionalista, e as técnicas de pesquisa Bibliográfica e Legislativa com o intuito de verificar as semelhanças e/ou divergências e sua funcionalidade, de forma a possibilitar a identificação das operações e estruturas de cada um dos subsistemas. Os resultados demonstraram a ocorrência de acoplamento estrutural entre os Subsistemas quanto à operacionalização da proteção do meio ambiente e da execução de ações de saúde no que se refere ao tema água com qualidade ao identificar-se a irritação das operações. Evidenciou-se que as estruturas acopladas realizam operações apoiadas em objetivos, princípios, diretrizes e sistemas de fiscalização e controle sobre o mesmo objeto, quanto à intenção de ofertar qualidade de vida para a população, por meio de processos e condições que procuram garantir qualidade para a água; seja no espaço natural sobre a utilização dos recursos naturais ou mesmo sobre aqueles de prestação de serviço de acesso a água que visam proteger os recursos hídricos de forma a disporem sobre maneiras de gestão e proteção desta para que possua qualidade para diferentes usos, e, consequentemente, segurança para ser servida como potável para o consumo realizado pela população. Dessa forma, foi confirmada a hipótese principal desse estudo, qual seja, a ocorrência de acoplamento de operações das estruturas do Subsistema Jurídico Ambiental, relacionadas à qualidade de vida da população brasileira por meio da proteção do meio ambiente, e do Subsistema Jurídico de Saúde, quanto à prática de prevenção e controle dos fatores de risco à saúde decorrentes do meio ambiente que possam prejudicar a qualidade de vida da população. / The present thesis presents an approach on identifying the occurrence of structural coupling between operations of the Legal Environmental Subsystems and Legal Health of the Brazilian Legal System. Therefore, it was used quality water, safe for human consumption as an operation to understand if there are irritations between the structures of these subsystems. The Social Systems of Niklas Luhmann's are used as the base theory, in particular the Law as a Social System, for self-description of the subsystems in order to apply the comparison and identification of the irritations between the structures that cause the structural coupling. The method of systemic approach was used, intending as a comparison between the subsystems by performing twenty-four rules of self-referencing. Methods of Comparative and Functionalist Procedure and the techniques of Bibliographic and Legislative research were also used in order to verify the similarities and/or divergences and their functionality, allowing the identification of the operations and structures of each subsystem. The results demonstrated the occurrence of structural coupling between subsystems on the implementation of environmental protection and the implementation of health actions on the theme quality of water, by identifying the irritation of operations. It was evidenced that the coupled structures perform operations based on objectives, principles, guidelines and monitoring systems and control over the same object, about the intention of offering quality of life for the population, by means of processes and conditions that seek to guarantee quality of water; be it, in natural environment when of the use of natural resources or even on those providing water access services which aim to protect the water resources in order to provide the ways of managing and protecting its quality for different uses, and, consequently, the security for it to be safely provided for population consumption. Thus, the main hypothesis of this study was confirmed, that is, the occurrence of coupling operations on the structures of the Legal Environmental Subsystem, related to the quality of life of the Brazilian population by means of protection of the environment, and, of the Legal Subsystem of Health, as for the practice of prevention and control of health risk factors resulting in an environment that could cause prejudice to the quality of life of the population.

Made available in DSpace on 2016-04-26T20:20:10Z (GMT). No. of bitstreams: 1 Fabio Nieves Barreira.pdf: 969684 bytes, checksum: b8dd4e09391c1fe39324724a887eafb5 (MD5) Previous issue date: 2011-06-08 / This dissertation aims to demonstrate that the Republic Constitution protects the value ecologically balanced environment, understood as the balance between being and environment, depending on natural selection, as a condition to healthy living. For the realization of constitutional values, the Highest Law imposes to political entities the duty to grant preferential treatment to products and services, and their development and delivery processes, as the environmental impact they cause to the environment. The tribute is an outstanding instrument to the protection of ecologically balanced environment, providing the environmental and tributaries principles of the Constitution that delimit the scope of environmental taxation, creating an environmental tax constitutional subsystem. Thus, political entities shall provide differential tax treatment through selectivity, progressivity and tax benefits, to products and services and their development and provision processes, according to the intensity of the environmental impact to the environment that they cause, demonstrated by a study of environmental impact, affecting the behavior of the market to develop in a sustainable way and granting to the property its social function. They must also collect taxes whose incidence allows the protection of ecologically balanced environment / A presente dissertação tem por fim demonstrar que a Constituição da República protege o valor meio ambiente ecologicamente equilibrado, assim entendido como a relação equilibrada entre o ser e o meio, em função da seleção natural, como condição à vida saudável. Para a realização do valor constitucional, a Lei Maior impõe aos entes políticos o dever de conceder tratamento diferenciado a produtos e serviços e a seus processos de elaboração e prestação, conforme o impacto ambiental que ocasionam ao meio ambiente. O tributo é instrumento de destaque à proteção do meio ambiente ecologicamente equilibrado, dispondo a Constituição de princípios ambientais e tributários que delimitam o âmbito da tributação ambiental, formando um subsistema constitucional tributário ambiental. Nesse passo, os entes políticos têm o dever de conferir tratamento tributário diferenciado, através de seletividade, progressividade e benefícios fiscais, aos produtos e serviços e seus processos de elaboração e prestação, na intensidade do impacto ambiental que ocasionem ao meio ambiente, demonstrado por estudo de impacto ambiental, condicionando o comportamento do mercado a se desenvolver de maneira sustentável e outorgando à propriedade a sua função social. Também é dever instituir tributos cuja regra matriz de incidência permite a proteção do meio ambiente ecologicamente equilibrado

The importance of quantum error correction in paving the way to build a practical quantum computer is no longer in doubt. Despite the large body of literature in quantum coding theory, many important questions, especially those centering on the issue of "good codes" are unresolved. In this dissertation the dominant underlying theme is that of constructing good quantum codes. It approaches this problem from three rather different but not exclusive strategies. Broadly, its contribution to the theory of quantum error correction is threefold. Firstly, it extends the framework of an important class of quantum codes - nonbinary stabilizer codes. It clarifies the connections of stabilizer codes to classical codes over quadratic extension fields, provides many new constructions of quantum codes, and develops further the theory of optimal quantum codes and punctured quantum codes. In particular it provides many explicit constructions of stabilizer codes, most notably it simplifies the criteria by which quantum BCH codes can be constructed from classical codes. Secondly, it contributes to the theory of operator quantum error correcting codes also called as subsystem codes. These codes are expected to have efficient error recovery schemes than stabilizer codes. Prior to our work however, systematic methods to construct these codes were few and it was not clear how to fairly compare them with other classes of quantum codes. This dissertation develops a framework for study and analysis of subsystem codes using character theoretic methods. In particular, this work established a close link between subsystem codes and classical codes and it became clear that the subsystem codes can be constructed from arbitrary classical codes. Thirdly, it seeks to exploit the knowledge of noise to design efficient quantum codes and considers more realistic channels than the commonly studied depolarizing channel. It gives systematic constructions of asymmetric quantum stabilizer codes that exploit the asymmetry of errors in certain quantum channels. This approach is based on a Calderbank- Shor-Steane construction that combines BCH and finite geometry LDPC codes.