Low-density parity-check (LDPC) codes have been shown to have good error correcting performance approaching Shannon’s limit. Good error correcting performance enables efficient and reliable communication. However, a LDPC code decoding algorithm needs to be executed efficiently to meet cost, time, power and bandwidth requirements of target applications. The constructed codes should also meet error rate performance requirements of those applications. Since their rediscovery, there has been much research work on LDPC code construction and implementation. LDPC codes can be designed over a wide space with parameters such as girth, rate and length. There is no unique method of constructing LDPC codes. Existing construction methods are limited in some way in producing good error correcting performing and easily implementable codes for a given rate and length. There is a need to develop methods of constructing codes over a wide range of rates and lengths with good performance and ease of hardware implementability. LDPC code hardware design and implementation depend on the structure of target LDPC code and is also as varied as LDPC matrix designs and constructions. There are several factors to be considered including decoding algorithm computations,processing nodes interconnection network, number of processing nodes, amount of memory, number of quantization bits and decoding delay. All of these issues can be handled in several different ways. This thesis is about construction of LDPC codes and their hardware implementation. LDPC code construction and implementation issues mentioned above are too many to be addressed in one thesis. The main contribution of this thesis is the development of LDPC code construction methods for some classes of structured LDPC codes and techniques for reducing decoding time. We introduce two main methods for constructing structured codes. In the first method, column-weight two LDPC codes are derived from distance graphs. A wide range of girths, rates and lengths are obtained compared to existing methods. The performance and implementation complexity of obtained codes depends on the structure of their corresponding distance graphs. In the second method, a search algorithm based on bit-filing and progressive-edge growth algorithms is introduced for constructing quasi-cyclic LDPC codes. The algorithm can be used to form a distance or Tanner graph of a code. This method could also obtain codes over a wide range of parameters. Cycles of length four are avoided by observing the row-column constraint. Row-column connections observing this condition are searched sequentially or randomly. Although the girth conditions are not sufficient beyond six, larger girths codes were easily obtained especially at low rates. The advantage of this algorithm compared to other methods is its flexibility. It could be used to construct codes for a given rate and length with girths of at least six for any sub-matrix configuration or rearrangement. The code size is also easily varied by increasing or decreasing sub-matrix size. Codes obtained using a sequential search criteria show poor performance at low girths (6 and 8) while random searches result in good performing codes. Quasi-cyclic codes could be implemented in a variety of decoder architectures. One of the many options is the choice of processing nodes interconnect. We show how quasi-cyclic codes processing could be scheduled through a multistage network. Although these net-works have more delay than other modes of communication, they offer more flexibility at a reasonable cost. Banyan and Benes networks are suggested as the most suitable networks. Decoding delay is also one of several issues considered in decoder design and implementation. In this thesis, we overlap check and variable node computations to reduce decoding time. Three techniques are discussed, two of which are introduced in this thesis. The techniques are code matrix permutation, matrix space restriction and sub-matrix row-column scheduling. Matrix permutation rearranges the parity-check matrix such that rows and columns that do not have connections in common are separated. This techniques can be applied to any matrix. Its effectiveness largely depends on the structure of the code. We show that its success also depends on the size of row and column weights. Matrix space restriction is another technique that can be applied to any code and has fixed reduction in time or amount of overlap. Its success depends on the amount of restriction and may be traded with performance loss. The third technique already suggested in literature relies on the internal cyclic structure of sub-matrices to achieve overlapping. The technique is limited to LDPC code matrices in which the number of sub-matrices is equal to row and column weights. We show that it can be applied to other codes with a lager number of sub-matrices than code weights. However, in this case maximum overlap is not guaranteed. We calculate the lower bound on the amount of overlapping. Overlapping could be applied to any sub-matrix configuration of quasi-cyclic codes by arbitrarily choosing the starting rows for processing. Overlapping decoding time depends on inter-iteration waiting times. We show that there are upper bounds on waiting times which depend on the code weights. Waiting times could be further reduced by restricting shifts in identity sub-matrices or using smaller sub-matrices. This overlapping technique can reduce the decoding time by up to 50% compared to conventional message and computation scheduling. Techniques of matrix permutation and space restriction results in decoder architectures that are flexible in LDPC code design in terms of code weights and size. This is due to the fact that with these techniques, rows and columns are processed in sequential order to achieve overlapping. However, in the existing technique, all sub-matrices have to be processed in parallel to achieve overlapping. Parallel processing of all code sub-matrices requires the architecture to have the number of processing units at least equal to the number sub-matrices. Processing units and memory space should therefore be distributed among the sub-matrices according to the sub-matrices arrangement. This leads to high complexity or inflexibility in the decoder architecture. We propose a simple, programmable and high throughput decoder architecture based on matrix permutation and space restriction techniques. / Thesis(Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2007

Calif., Univ., Dep. of Economics, Diss.--Stanford, 2002. / Kopie, ersch. im Verl. UMI, Ann Arbor, Mich.

Univ., Diss.--Bonn, 2002.

Univ., Fak. für Wirtschaftswiss., Diss.--Magdeburg, 2002. / Literaturverz. S. [269] - 296.

This thesis present an efficient approach for performing smoke simulation on curvilinear grids. The solution of the Navier-Stokes equations on curvilinear is made on three steps: advection, pressure solving and velocity projection. The proposed advection method is simple, fast and unconditionally-stable. Our solution is able to maintain a staggered-grid variable arrangement, and includes an efficient solution to enforce mass conservation. Compared to approaches based on regular grids traditionally used in computer graphics, our method allows for better representation of boundary conditions, lending to more realistic results, with just a small increment in computational cost. Moreover, we are able to condensate cells where interesting artifacts tend to appear, like swirling vortices or turbulence. We demonstrate the effectiveness of our approach, both in 2-D and 3-D, through a variety of high-quality smoke simulations and animations. These examples show the integration of our method with overlapping grids and multigrid techniques.

This thesis present an efficient approach for performing smoke simulation on curvilinear grids. The solution of the Navier-Stokes equations on curvilinear is made on three steps: advection, pressure solving and velocity projection. The proposed advection method is simple, fast and unconditionally-stable. Our solution is able to maintain a staggered-grid variable arrangement, and includes an efficient solution to enforce mass conservation. Compared to approaches based on regular grids traditionally used in computer graphics, our method allows for better representation of boundary conditions, lending to more realistic results, with just a small increment in computational cost. Moreover, we are able to condensate cells where interesting artifacts tend to appear, like swirling vortices or turbulence. We demonstrate the effectiveness of our approach, both in 2-D and 3-D, through a variety of high-quality smoke simulations and animations. These examples show the integration of our method with overlapping grids and multigrid techniques.

O CODIVAR (Consórcio de Desenvolvimento Intermunicipal do Vale do Ribeira) e o CONSAD (Consórcio de Segurança Alimentar e Desenvolvimento Local) são dois instrumentos de ação pública criados no Vale do Ribeira - SP com o objetivo de promover cooperação para o desenvolvimento, a partir de diferentes referências. No caso do CODIVAR, sua origem é bottom-up a partir de iniciativa voluntária dos prefeitos e da influência externa do nível estadual representado por Franco Montoro e seus ideais progressistas; é configurado em uma estrutura decisória restrita aos prefeitos. No caso do CONSAD, sua origem é top-down a partir do contexto das políticas de desenvolvimento territorial propostas pelo nível federal representado por Lula e fundamentado pela retórica participativa de seu discurso eleitoral; é configurado em uma estrutura decisória que concede poder de participação e capacidade de deliberação para a sociedade civil, proporcionando-lhe protagonismo. Ao longo do tempo e do movimento de interação com os atores que se apropriaram destes instrumentos de acordo com suas lógicas e interesses, os objetivos que motivaram sua criação mudaram de trajetória. Assim, os instrumentos passaram a ser inercialmente conduzidos, assumindo vida própria a partir de novas representações. Este movimento de apropriação do espaço do Vale do Ribeira pelos atores permitiu a construção social de dois territórios sobrepostos, organizados por conexões e lógicas de atuação distintas (embora igualmente amesquinhadas) que geram tensões e impossibilidade de articulação e cooperação. Além disso, este movimento permite entender como foram construídas relações de atraso no interior destes instrumentos. No caso do CODIVAR, tais relações explicam sua capacidade de permanência legitimada no espaço de ação pública do Vale do Ribeira, enquanto no CONSAD desenharam caminhos que levaram ao esvaziamento do fórum. / CODIVAR (Intermunicipal Consortium for the Development of the Ribeira Valley) and CONSAD (Consortium for Food Security and Local Development) and are two public action instruments created in the Ribeira Valley, São Paulo state, Brazil, with the aim of promoting cooperation for development from different references. In the case of CODIVAR, its origin is \"bottom-up\" from voluntary initiative of the mayors and the external influence of the state level government represented by Franco Montoro and his progressive ideals; It is set in a decision-making structure restricted to mayors. In the case of CONSAD, its origin is \"top-down\" from the context of territorial development policies proposed by the federal level represented by Lula and grounded by the participatory rhetoric of his election speech; It is set in a decision-making structure that empowers participation and deliberation capacity for civil society, making it the protagonist. Over time and throughout the movement of interaction with the actors who have appropriated these instruments according to their logic and interests, the goals that motivated instruments creation changed their trajectory. Thus, the instruments started being inertially conducted, taking life from new representations. This appropriation movement of the Ribeira Valley by the actors allowed the social construction of two overlapping territories, organized by distinct connections and logics of action (though both contaminated by personal and political interests) that generate tension and impossibility of articulation and cooperation. Furthermore, this movement allows to understand how delayed relations were constructed within these instruments. In the case of CODIVAR such relations explain its legitimate staying power in public action space of the Ribeira Valley, while in CONSAD such relations drew paths that led the forum to emptying process.

This thesis present an efficient approach for performing smoke simulation on curvilinear grids. The solution of the Navier-Stokes equations on curvilinear is made on three steps: advection, pressure solving and velocity projection. The proposed advection method is simple, fast and unconditionally-stable. Our solution is able to maintain a staggered-grid variable arrangement, and includes an efficient solution to enforce mass conservation. Compared to approaches based on regular grids traditionally used in computer graphics, our method allows for better representation of boundary conditions, lending to more realistic results, with just a small increment in computational cost. Moreover, we are able to condensate cells where interesting artifacts tend to appear, like swirling vortices or turbulence. We demonstrate the effectiveness of our approach, both in 2-D and 3-D, through a variety of high-quality smoke simulations and animations. These examples show the integration of our method with overlapping grids and multigrid techniques.

Submitted by Haroudo Xavier Filho (haroudo.xavierfo@ufpe.br) on 2016-03-01T16:57:56Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) 2015, Desoneração da folha de pagamentos -final- Carlos Eduardo - final.pdf: 1472443 bytes, checksum: 40ab31bfa833ed1d099a25ceb24fc326 (MD5) / Made available in DSpace on 2016-03-01T16:57:56Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) 2015, Desoneração da folha de pagamentos -final- Carlos Eduardo - final.pdf: 1472443 bytes, checksum: 40ab31bfa833ed1d099a25ceb24fc326 (MD5) Previous issue date: 2015-06-13 / CAPES / Neste trabalho, apresentaremos políticas tributárias com o intuito de avaliar o impacto de longo prazo da desoneração da folha de pagamentos sobre consumo agregado, o estoque de capital, produto e o bem-estar entre gerações. Para isso, utilizaremos o modelo de gerações sobrepostas (Overlapping Generations Models) com vida finita, probabilidade de morte e previdência social. A inovação dessa pesquisa frente a literatura, foi a simulação com alíquota zero sobre a contribuição patronal, a incorporação da despesa da previdência e do fator previdenciário. Com essas modificações, temos um modelo próximo da economia brasileira. Os resultados apontaram que a desoneração da folha de pagamentos provocou aumentos no produto, capital e consumo de longo prazo, sem grandes sacrifícios para a economia no curto prazo. / In this work, we present tax policies in order to assess the impact of long-term relief payroll on aggregate consumption, the stock of capital, product and welfare between generations. For this, we use the model of overlapping generations with finite life, risk of death and social security. The innovation of this research literature forward was the simulation with zero tax rate on the employer's contribution, the incorporation of the social security expense and the social security factor. With these changes, we have a model close to the Brazilian economy. The results showed that the relief payroll caused increases in product, capital and long-term consumption without major sacrifice for the economy in the short term.

L’hypothèse de gènes chevauchants codés par le brin antisens des rétrovirus est un concept ancien. Cependant, celui-ci n’a été réellement démontré qu’il y a une dizaine d’années avec la découverte de la protéine HBZ du virus HTLV-1 et les résultats récents sur la protéine ASP du VIH-1. Les nouvelles recherches sur cette protéine ont démontré son expression in vivo, mais sa fonctionnalité est toujours inconnue. Nous avons réalisé ici, à partir d’un jeu de données de plus de 20 000 séquences, les premières analyses bioinformatiques sur l’évolution de ce gène chevauchant. Nous avons alors montré que le gène asp est conservé uniquement dans les séquences du groupe M correspondant au groupe pandémique du VIH-1. Nous démontrons de plus, une corrélation entre la présence de l’ORF ASP et la prévalence des différents groupes et sous-types. Nos analyses phylogénétiques montrent que l’apparition de l’ORF ASP est concomitante avec l’émergence de la pandémie du groupe M. Du fait du chevauchement de gènes, l’analyse de la pression de sélection induite par la protéine ASP a impliqué l’utilisation de modèles et de méthodes d’analyses spécifiques. Situé sur la phase -2, ce chevauchement entraîne une correspondance des troisièmes bases des codons de chaque gène. Si on considère un gène « fixe », les contraintes mécaniques induites par ce gène sont très importantes et le gène chevauchant dispose de très peu de flexibilité. Il est alors important d’identifier la pression de sélection propre au gène situé sur la phase -2, et montrer ainsi que sa présence et sa conservation ne sont pas seulement dues aux contraintes induites par le gène fixe. Pour cela, nous avons tout d’abord montré par des analyses de simulations de séquences, à l’aide d’un modèle à codon, que la présence de l’ORF ASP n’est pas due au hasard. Nous avons ensuite développé une méthode d’analyse évolutive basée sur l’étude des mutations silencieuses pour le gène fixe (ici le gène env) entraînant l’apparition ou la disparition des codons Start et Stop sur le gène chevauchant. L’application de cette méthode au gène asp montre qu’il existe bien une pression de sélection induite par la protéine ASP. / The hypothesis of overlapping genes encoded by the antisense strand of the retrovirus is an old concept. However, this one has been really demonstrated that with the discovery of the HBZ protein of HTLV-1 virus, a dozen of years ago and the recent results on the ASP protein of HIV-1. New research on this protein has demonstrated its expression in vivo, but its functionality is still unknown. We performed here, from a data set of more than 20,000 sequences, the first bioinformatic analyses on the evolution of this overlapping gene. We showed that the asp gene is conserved only in the M group sequences corresponding to the pandemic group of HIV-1. Moreover, we demonstrated a correlation between the presence of the ASP ORF and the prevalence of the various groups and subtypes. Our phylogenetic analyses showed that the appearance of the ASP ORF is concomitant with the emergence of the pandemic M group. Because of the overlapping of the genes, the analysis of the selection pressure induced by the ASP protein involved the use of models and specific analysis methods. Located in the frame -2, this overlap induces a correspondence of the third base codon of each gene. If we consider a "fixed" gene, the mechanical constraints induced by this "fixed" gene are very important and the overlapping gene has very little flexibility. Then, it is important to identify the selection pressure of the gene which is in the frame -2 and show that its presence and conservation are not only due to mechanical constraints induced by the "fixed" gene. For this, we first demonstrated by sequence simulation analysis, using a codon model, that the presence of the ASP ORF is not due to chance. Then, we developed a method of evolutionary analysis based on the study of synonymous mutations in the "fixed" gene (here the env gene) causes the appearance or disappearance of start and stop codons in the overlapping gene. When we applied this method to the asp gene, it showed that there is a selection pressure induced by the ASP protein.