Particle image velocimetry technique for analysis of retractibility in woods of Pinus elliottii

The aim of this work was to verify the ability to use the Particle Image Velocimetry technique for measurements of dimensional variations resulting from wood retractability of Pinus elliottii wood, initially saturated and with the surface marked with multiple dots of ink randomly distributed, was used in this work to apply the Particle Image Velocimetry technique. The specimens were dried and images were captured during the process. The images obtained were processed by the Particle Image Velocimetry algorithm and the deformations that occurred were calculated. For comparison, a conventional method (pachymeter) was used to measure the dimensions of the specimen during drying. The variation in dimensions obtained on the surface of the specimens from the Particle Image Velocimetry technique was 2,28 % for the radial direction and 0,20 % for the longitudinal direction of the fibers. With the standardized method, these values ​​were 2,18 % for the radial direction and 0,21 % for longitudinal. The reduction in the average area of ​​the specimens was 3,85 % by the Particle Image Velocimetry technique and 3,77 % by the conventional methodology. It was concluded that the Particle Image Velocimetry technique was able to accurately measure the displacements on the surface of the Pinus elliottii specimens, resulting in values ​​statistically similar to those reached through the use of the conventional measurement method, demonstrating its reliability.           &nbsp

Sampling rate in the dynamic speckle analysis

Dynamic laser speckle and its biological version (biospeckle laser) have been used in many areas of knowledge. Its noninvasive approach allows the application in advantage regarding those that need contact or damage the analyzed sample. However, one needs the sharp adjust of the image acquiring and processing. In this article, we show how the variation of sampling rate in a dynamic speckle analysis affects the value of dynamic speckle indexes concerning the absolute value of the differences index, the temporal speckle standard deviation index, and the temporal speckle mean index. We show that the dynamic speckle index value changes its maximum excursion with the variation of sampling rate, affected directly by the camera's time integration (time of exposure). We highlight the importance of knowing the frequency band of the analyzed phenomenon and its signal to choose the appropriate sampling rate, with the recommendation of using the lowest sampling rate possible¿without compromise the speckle grains¿to obtain an acceptable maximum excursion and an illumination level with a good signal-noise ratio. The results will help those who work with the phenomenon/technique to enhance their analysis tailoring the set up and yielding reliable results, since the optical method demands a rigorous bias of the image acquiring and processing

Bit-flipping algorithms for joint decoding of correlated sources in noisy channels

Orientador: Jaime PortugheisTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Esta tese propõe um sistema de transmissão de informação de várias fontes correlacionadas sobre canais ruidosos. Inicialmente se aborda o problema da codificação fonte-canal conjunta. Para este problema se definirá conceitos de taxas ótimas e se apresentará a maneira de obtê-las. Posteriormente, será proposto um algoritmo de decodificação conjunta com complexidade tratável. Diversos resultados de desempenho do algoritmo proposto serão apresentados. Estes resultados mostram um bom compromisso entre desempenho e complexidade quando comparados com a decodificação independente. Finalmente, o algoritmo de decodificação conjunta seguido de uma proposta de regra de fusão é usado no problema CEO e o desempenho deste novo algoritmo é apresentadoAbstract: This thesis proposes a system that transmits information from various correlated sources over noisy channels. Initially, it addresses the problem of joint source-channel coding. To solve this problem, concepts of optimal rates will be defined and the way to obtain them will be presented. Subsequently, a joint decoding algorithm with a tractable complexity is proposed. Several performance results of the proposed algorithm will be presented. These results show a good compromise between performance and complexity when compared to the non-joint decoding. Finally, the joint decoding algorithm, followed by a proposal for a fusion rule is used in the CEO problem and the performance of this new algorithm is presentedDoutoradoTelecomunicações e TelemáticaDoutor em Engenharia Elétric

Hard decision algorithms for LDGM Codes

Orientador: Jaime PortugheisDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Desde que Gallager introduziu o algoritmo de decodificação Bit-Flipping (BF) com decisão abrupta para códigos Low Density Parity Check (LDPC), outras duas variantes foram propostas por Sipser e Spielman para os códigos conhecidos como "Expander Codes". Posteriormente, uma versão da decodificação BF por decisão suave conhecida como decodificação Modified Weighted BF (MWBF), foi investigada. Esta tese propõe versões modificadas dos algoritmos de Sipser e Spielman. Resultados de simulações para códigos Low Density Generator Matrix (LDGM) sistemáticos, com comprimento longo mostraram um melhor desempenho da versão proposta. Adicionalmente, para um comprimento médio dos códigos LDGM, resultados de simulações mostraram um desempenho similar à decodificação MWBF com a vantagem de não ser necessário o uso de operações em ponto flutuanteAbstract: Since Gallager introduced Bit-Flipping (BF) decoding with hard-decision for Low-Density Parity- Check Codes (LDPC), other two variants were proposed by Sipser and Spielman for expander codes. Later, a soft-decision version of BF decoding, known as Modified Weighted BF (MWBF) decoding, was investigated. This thesis proposes modified versions of Sipser and Spielman algorithms. Simulation results for long systematic Low-Density Generator Matrix (LDGM) codes show a better performance of the proposed versions. Moreover, for moderate length systematic LDGM codes, simulation results show performance similar to that of MWBF decoding with the advantage of not requiring floating-point operationsMestradoTelecomunicações e TelemáticaMestre em Engenharia Elétric