Lic.-avh. Karlskrona : Blekinge tekniska högskola, 2010.

Thesis (M.S.)--University of Wisconsin--Madison, 1980. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 65-68).

Thesis (Ph. D.)--University of Massachusetts Amherst, 2009. / Open access. Includes bibliographical references (p. 253-262). Print copy also available.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed on Nov. 13, 2006). PDF text: xi, 124 p. : ill. (some col.) ; 0.56Mb. UMI publication number: AAT 3215056. Includes bibliographical references. Also available in microfilm and microfiche format.

TCC(graduação) - Universidade Federal de Santa Catarina. Centro Tecnológico. Ciências da Computação. / Submitted by Pedro Henrique Lenzi Soares null (p.h.lenzi.soares@grad.ufsc.br) on 2017-07-11T20:13:57Z No. of bitstreams: 1 Federal_University_of_Santa_Catarina__UFSC__Thesis (1).pdf: 555247 bytes, checksum: 2e30103f337e5dc9ba6ede17eb321551 (MD5) / Approved for entry into archive by Renato Cislaghi (renato.cislaghi@ufsc.br) on 2017-07-23T14:44:40Z (GMT) No. of bitstreams: 1 Federal_University_of_Santa_Catarina__UFSC__Thesis (1).pdf: 555247 bytes, checksum: 2e30103f337e5dc9ba6ede17eb321551 (MD5) / Made available in DSpace on 2017-07-23T14:44:40Z (GMT). No. of bitstreams: 1 Federal_University_of_Santa_Catarina__UFSC__Thesis (1).pdf: 555247 bytes, checksum: 2e30103f337e5dc9ba6ede17eb321551 (MD5) Previous issue date: 2017-06-12 / As áreas de estudo em criptografia e certificação digital apresentam diversas ferramentas que poderiam ser utilizadas como mecanismos de comprovação de identidade e autenticação por uma larga variedade de softwares. Não obstante, é comumente custoso para o time de desenvol- vimento implementar tais ferramentas de forma fácil de usar e o mais portável possível. O objetivo principal desta tese é criar ferramentas que podem ser facilmente integradas com a maior variedade de softwa- res possível, mantendo o menor número possível de dependências, para minimizar o esforço que os usuários precisam fazer para ter acesso à funcionalidades de criptografia e certificação digital. As soluções aqui apresentadas como resultado deste estudo foram testadas e integradas em um software existente, para que o processo de integração pudesse ser descrito de forma mais precisa.

Orientador : Dalton Soares Arantes / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica / Made available in DSpace on 2018-07-14T03:40:47Z (GMT). No. of bitstreams: 1 Bezerra_JoaoBatista_D.pdf: 8425830 bytes, checksum: 43ce5296f9679f1e1ba223943191cc6b (MD5) Previous issue date: 1987 / Resumo: Os sistemas de modulação codificada que usam Códigos convolucionais para controlar a transmissão dos símbolos associados à modulação, são estudados utliIizando uma abordagem que se fundamenta no modeIamento do codificador associado ao código convolucional como uma máquina seqüencial de Mealy. o modelo desenvolvido é utilizado na otimização de códigos convolucionais a serem usados em conjunção com uma dada constelação de sinais, cuJos símbolos são supostos pertencerem a um espaço multidimensional. Este mesmo modelo é uti lizado para avaliar as propriedades espectrais de sinais codimodulados e, desta forma, determinar o efeito da dimensional Idade na faixa de transmissão. o desempenho dos códigos selecionados é obtido por meio de simulação do sistema, como também por meio de aproximações para as probabilidades de erro de evento e de bit / Abstract: Not informed. / Doutorado / Doutor em Engenharia Elétrica

M.Ing. / The objective of this research is to develop a new robust and efficient adaptive watermarking method for JPEG compressed images, in which the watermark can survive even if the watermarked image undergoes manipulations. In this thesis, we present two image watermarking methods: one based on the spatial domain and the other on the DCT-based domain. Both approaches, which embed meaningful information into images for copyright protection, are blind watermarking schemes. To illustrate the robustness and performance enhancement derived from Error Correction Codes (ECC) when applied to watermarking, we propose Method I based on the Direct Sequence Spread Spectrum (DSSS) technique in conjunction with Reed-Solomon codes for raw images in the spatial domain. As is evident from our results, the introduction of Reed- Solomon codes improves the robustness of a watermark. Also, employing the properties of pseudo-noise (PN) to deal with cropping attacks is investigated for this method. Based on Method I, we propose Method II that takes into account the properties of JPEG images and exploits the advantages of error correction codes (ECC). Furthermore, some modifications are introduced in the basic Spread Spectrum watermarking to improve the accuracy of the watermark retrieval process. Several experimental results are provided to demonstrate the performance of the proposed schemes. In these experiments, JPEG compression, cropping, brightness/contrast adjustment, median filtering and noise addition are used as watermark attacks to evaluate the robustness. The experimental results show that the proposed scheme (Method II) is very robust against common image processing attacks.

M.Ing. (Electrical Engineering) / As the demand for high-speed data communications over conventional channels such as coaxial cables and twisted pairs grows, it becomes neccesary to optimize every aspect of the communication system at reasonable cost to meet this demand effectively. The choice of a line code is one of the most important aspects in the design of a communications system, as the line code determines the complexity, and thus also the cost, of several circuits in the system. It has become known in recent years that a multilevel line code is preferable to a binary code in cases where high-speed communications are desired. Apart from ternary codes, not many multilevel codes are available. Some of the existing line codes also suffer from serious drawbacks regarding a lack of complying to input restrictions, small values of efficiency, and great code complexity. In this study, Markov models and values of channel capacity are presented for several classes of restricted multilevel sequences which are thought to be of practical importance in view of the channel input restrictions that these codes satisfy. Different coding methods are used to construct low-complexity encoders and decoders for generating and decoding these sequences with high values of efficiency, good error behaviour and favourable power spectral densities

Orientador: Yuzo Iano / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica / Made available in DSpace on 2018-07-19T10:18:32Z (GMT). No. of bitstreams: 1 Nascimento_AyresMardemAlmeidado_M.pdf: 6592482 bytes, checksum: a7a382134a80aee599937f19e9d6a1ed (MD5) Previous issue date: 1994 / Resumo: Neste trabalho, apresentam-se estudos relacionados com a redução da taxa de bits de transmissão do sinal digital de televisão P AL - M (Phase Alternation Line-Padrão M), adotado no Brasil, através da simulação em computador, de um sistema de redução de taxa que usa a técnica MCPD (Modulação por Código de Pulso Diferencial), baseado em uma arquitetura de dois canais, utilizando o padrão de campo quincunx. Foram implementados alguns preditores baseados no mosaico de fase das amostras, obtido com a frequência de amostragem ¿f IND. alfa¿ = ¿4 f IND. SC¿ (¿f IND. SC é a frequência da subportadora de cor), com o objetivo de se fazer a previsão correta em áreas uniformes e alcançar a taxa desejada de 34 e 68 Mbit/s compatíveis com a terceira hierarquia MCP padronizado pelo CCIR. Foram estudados também, alguns quantizadores não lineares eficientes. São apresentados ainda, aspectos relevantes relacionados com os filtros digitais do tipo FIR (Finite Impulse Response) utilizados na composição e decomposição de sinais de Televisão. Outros modelos foram também estudados para efeito comparativo. Realizou-se simulações com os modelos, utilizando-se sinais padronizados pelo CCIR e pela SMPTE, para análises objetivas e subjetivas dos resultados, principalmente em termos de entropia, taxa de bits, relação sinal/ruído e visualização dos sinais recuperados / Abstract: Not informed. / Mestrado / Mestre em Engenharia Elétrica

Biodiversity information is critical to inform science-based policy development as well as to support responsible and accountable land-use planning and decision-making practices. The uptake of available information for these uses is, however, not yet quantified or understood. Here, the extent to which the needs of biodiversity information end-users in South Africa are supported via existing information sources was investigated, at the science, practice and policy interface, using the South African National Biodiversity Institute (SANBI's) online conservation mapping service users as a case study. A quantitative investigation of the information needs of end-users of biodiversity information was made, their information-seeking patterns analysed and the various uses of information by different user groups in South Africa investigated. This allowed for the implications of these needs and behaviour on system design and information provision to be formulated to better design the envisaged National Biodiversity Information System at SANBI. Based on a representative sample of end-users from policy, implementation and research backgrounds, a questionnaire was used and the responses were examined to determine which content was most useful, what barriers and enablers they face when trying to access biodiversity information, and what degree of interdisciplinary information is needed in addressing environmental problems. A sample of 778 (13%) respondents from a total of 5977 biodiversity information users was analysed from across the country. The study found that the lack of appropriate or available information remains one of the three highest unmet needs of biodiversity information end-users. The absence of good prior knowledge of sources of biodiversity information and unreliable and inaccurate information are two additional factors that hinder respondents in finding biodiversity information and achieving their goals. The major implication of information deficiency identified by respondents related to uncertain and/or inaccurate outcomes resulting in ill-informed decision-making. A key outcome of the analysis of the survey results are a series of recommendations on how these issues might be addressed, and it is envisioned that these may be used to help guide the development of a National Biodiversity Information System. A broad range of recommendations have been proposed, principally that the interoperability of information from various adjacent and disparate fields of study be combined with biodiversity information as a means of addressing environmental problems.