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The main aim of the thesis is to find the optimal division of load in the three queues, i.e. the optimal degree of overlap of skills between the two servers with waiting time in queue as the performance measure. The model under consideration is a polling system with two servers and three queues - two specialized queues, 1 and 2, and a common queue, queue 3. One of the servers cycles between queues 1 and 3 and the other between 2 and 3. The imbedded Markov chain state equations and the functional equations for queue length probability generating functions are formulated. It was not possible to obtain a closed for expression for the exact mean waiting time in the queues by solving the functional equations. So, an attempt has been made to get an approximate closed form expression that could be used to find the optimal division of load in the three queues. Since the results are available only for the symmetric system we first assume the two specialized queues to be identical. But later we relax this assumption and give approximation method for the asymmetric system. The recommended method to approximate the mean waiting time in a queue can be used to determine the optimal allocation of load to the three queues. / Thesis / Master of Science (MSc)

Ce travail de thèse porte sur le développement d’outils de modélisation pour le contrôle non destructif (CND) par courants de Foucault (CF). Il existe actuellement une tendance à la mise en œuvre de capteurs souples qui représentent une solution pertinente pour inspecter des pièces ayant une surface complexe. L’objectif principal de cette thèse est l’élaboration de techniques permettant la modélisation de ce type de capteurs au sein de la méthode des éléments finis (MEF).Lors de la modélisation d’un capteur souple avec la MEF, trois problématiques se manifestent. La première concerne le maillage des milieux fins qui apparaissent dans ce type de configuration (distance capteur-pièce contrôlée, bobine plate, revêtement fin...). Le maillage de ces régions par des éléments simpliciaux peut poser des problèmes numériques (éléments déformés quand un maillage grossier est considéré et grand nombre d’inconnues quand un maillage fin est utilisé). La deuxième problématique concerne le déplacement du capteur. Si les différents sous-domaines géométriques (air, pièce, capteur...) sont convenablement remaillés pour chaque position du capteur, le temps total pourra être pénalisant. La troisième problématique relative à la modélisation d’un capteur souple porte sur l’imposition du courant dans des bobines déformées.Une comparaison de différentes approches nous a conduit à retenir la méthode overlapping, qui permet de considérer simultanément des milieux fins avec maillages non-conformes. Cette méthode permet d’effectuer le recollement de deux surfaces non planes et/ou de géométries différentes. La méthode overlapping a été implantée dans deux formulations duales (magnétique et électrique) en 2D et 3D intégrées dans le code de calcul DOLMEN (C++) du LGEP. La méthode overlapping a été validée pour la prise en compte de plusieurs types de régions minces (air, milieux conducteurs, milieux magnétiques, bobines plates...). La modélisation des capteurs souples nécessite aussi l’implantation d’une technique permettant d’imposer correctement les courants dans un inducteur de forme arbitraire. Une technique a été sélectionnée et programmée, d’abord pour des bobines classiques (volumiques) déformées puis pour des bobines plates flexibles. Afin de valider les développements réalisés, différentes configurations de test ont été traitées et les résultats comparés avec des solutions de référence analytiques ou expérimentales. / The objective of this thesis is the development of modeling tools for eddy current testing (ECT). Currently there is a tendency to use flexible sensors which represent a viable solution for inspecting parts with a complex surface. The main objective of this thesis is the development of techniques for taking into account this kind of sensors within the finite element method (FEM).When modeling a flexible sensor with the FEM, three issues have to be considered. The first one is related to the mesh of thin regions that appear in this kind of configuration (sensor-inspected part distance, thin coating...). The meshing of these regions with simplicial elements can cause numerical problems (distorted elements when a coarse mesh is considered and high number of unknowns when a fine mesh is used). The second issue is related to the displacement of the sensor on the part surface. If the different subdomains (air, part, sensor ...) are properly remeshed for each position of the sensor, the required time can be penalizing. The third issue, related to the modeling of a flexible sensor, is the computation of the current in distorted sensor coils.A comparison of different approaches has led to select the overlapping element method, which allows to simultaneously consider the thin regions with nonconforming meshes. This method allows to perform the connection of two surfaces which can be non-planar and/or have different geometries. The overlapping method has been implemented in two dual formulations (magnetic and electric) in 2D and 3D and integrated in the computation code (C++) DOLMEN of LGEP. The overlapping method has been validated for several kinds of thin regions (air, conductive regions, magnetic regions, flat coils...). The modeling of flexible sensors also requires the establishment of a technique for properly imposing the current in an inductor of arbitrary shape. A technique has been selected and implemented for conventional (volumic) distorted coils but also for flexible flat coils. Different test configurations have been considered in order to validate the developments and the results have been compared with analytical references or experimental solutions.

本研究利用台灣2001年資料以Ramsey與OLG假設分別建立區分四部門別與八部門別之動態可計算一般均衡模型，進行「提高間接稅（消費稅、環境稅）、降低直接稅（資本、勞動所得稅）」之稅制改革模擬分析。結果發現若以單一時點比較靜態方式分析可能迥異於動態長期分析結果；其次以Ramsey分析所欠缺的代際分配影響結果在OLG分析中可以察見，特別是進行以消費稅或環境稅替代資本所得稅模擬時；再者OLG因代際傳遞效果可能較Ramsey假設下反應緩慢，故也可觀察到Ramsey模型面對衝擊後若干變數增減幅度會較OLG模型陡峭。最後特別在環境稅替代所得稅模擬中經由替代稅率變化發現，活在初期世代雖可享受所得稅下降好處但卻也面臨排放稅課徵，因此福利水準增減變化不大，惟屆至排放稅課徵瀕至臨界點需使用原所得稅來平衡稅收時，此為另一波必須為減量政策付出代價的時點與世代。 / Based on a thorough comparison of the basic assumptions and economic underpinning of the Ramsey and Overlapping generation (OLG) model, this study builds both static and dynamic computable general equilibrium tax policy models to analyze the effect of tax reform on Taiwan’s economy. The new tax structure considers mainly a replacement of some parts of direct tax - labor and capital income taxes by indirect tax- consumption tax or environment tax. The benchmark year of the model is 2001, and the economy is divided into four and eight sectors. The modeling framework is implemented on top of MPSGE, which is a special module within the General Algebraic Modeling System (GAMS).Our simulation results show differential outcomes for static and dynamic models. The slower speed of transition inherent in OLG model has caused variables such as welfare, capital stock, and replacement consumption tax rate change less than that in the Ramsey model when the tax reform policy is imposed. And the intergeneration effects of different tax burden between young and old generations can be found in the OLG model but not in the Ramsey model. Finally, we find as the income tax rate coming lower and the environment tax going up when simulation of tax replacement, causing the welfare does not change much at the beginning of shock, and generations especially born in the near future when environment tax does not grow and revenue neutrality needs to be meet are another cost payers of abatement policy.

This research is mainly focused on the development of the adaptive Cartesian grid methods for compressibl  e flow. At first, the ghost cell method and its applications for inviscid compressible flow on adaptive tree Cartesian grid are developed. The proposed method is successfully used to evaluate various inviscid compressible flows around complex bodies. The mass conservation of the method is also studied by numerical analysis. The extension to three-dimensional flow is presented. Then, an h-adaptive Runge–Kutta discontinuous Galerkin (RKDG) method is presented in detail for the development of high accuracy numerical method under Cartesian grid. This method combined with the ghost cell immersed boundary method is also validated by well documented test problems involving both steady and unsteady compressible flows over complex bodies in a wide range of Mach numbers. In addition, in order to suppress the failure of preserving positivity of density or pressure, which may cause blow-ups of the high order numerical algorithms, a positivity-preserving limiter technique coupled with h-adaptive RKDG method is developed. Such a method has been successfully implemented to study flows with the large Mach number, strong shock/obstacle interactions and shock diffraction. The extension of the method to viscous flow under the adaptive Cartesian grid with hybrid overlapping bodyfitted grid is developed. The method is validated by benchmark problems and has been successfully implemented to study airfoil with ice accretion. Finally, based on an open source code, the detached eddy simulation (DES) is developed for massive separation flow, and it is used to perform the research on aerodynamic performance analysis over the wing with ice accretion.

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.

Made available in DSpace on 2016-03-15T19:46:55Z (GMT). No. of bitstreams: 1 Maria Andrade dos Santos.pdf: 2064830 bytes, checksum: 7e6cc7bb347daaeef85e015ba70f2ad1 (MD5) Previous issue date: 2010-02-08 / Having as initial objective to unmask the literature in the Internet, we cover the way of discovery through the Angela Lago’s workmanships: books and site. From this passage book to site, we can evidence that Angela Lago writer trod the way of the intertextuality, the visual and verbal overlapping, hypertext, a way that certainly would take it and it took it to the site. A site, as much others, where we can find image, sound, movement, and tridimensionality form, but this is what we can also find in her books, books with pictures/color/movement, words/sound. Showing the non-linear or multilinear form in the books, and the linear form on the site. For this dissertation we use the books: O Fio do Riso, and Chiquita Bacana e outras pequetitas. / Tendo como objetivo inicial desvendar a literatura na internet, percorremos o caminho da descoberta através das obras de Angela Lago, livros e site. A partir deste percurso livro-site, podemos constatar que Angela Lago escritora trilhava o caminho da intertextualidade, da sobreposição visual e verbal, do hipertexto, um percurso que certamente a levaria e a levou ao site. Um site, como tantos outros, onde podemos encontrar a imagem, o som, o movimento, e a tridimensionalidade, mas esta que também encontramos em seus livros, livros com imagens/cor/movimento, palavras/som. Mostrando desta forma a alinearidade dos livros, ou linearidades múltiplas, e linearidade do site. Para esta dissertação nos utilizamos dos livros: O Fio do Riso e Chiquita Bacana e outras pequetitas.

Environnement et activités humaines interagissent à travers des relations multiples et complexes. Cette thèse s’interroge sur les limites que l’environnement pourrait imposer à la croissance. Le premier chapitre montre que l’environnement peut constituer un frein au développement en diminuant l’espérance de vie des agents, en freinant leur épargne, et peut causer des situations de trappes à pauvreté environnementales. La mise en place de politiques environnementales publiques peut néanmoins permettre d’éviter ces trappes et d’augmenter le niveau de revenu par tête. Dans le second chapitre,l’existence de ressources non-renouvelables polluantes nécessaires à la production est susceptible de freiner la croissance. Cependant, dans la lignée des travaux néoclassiques des années 70, les difficultés liées au caractère fini des ressources peuvent être dépassées par un progrès technologique exogène et des possibilités de substitution capital-ressources suffisantes. Il est par ailleurs démontré qu’une pollution non-persistante provenant de l’utilisation des ressources ne constituait pas un frein au développement. Enfin, le troisième chapitre démontre qu’une forte dépendance aux ressources naturelles affecte négativement la croissance des pays en développement, tandis que l’abondance en ressources naturelles la favorise. La dépendance étant le résultat de choix économiques, une politique de diversification de l’économie consistant à réinvestir les rentes issues de l’exploitation des ressources naturelles dans les secteurs secondaire et tertiaire pourrait permettre de la réduire. Par ailleurs, nous suggérons que développer l’éducation, les institutions et les marchés financiers pourrait permettre de limiter le risque de malédiction des ressources. / Human activities and the environment interact through multiple and complex relations. Can the natural environment be viewed as a limit to growth ? This thesis tries to develop answers to this crucial question.The first chapter shows that environmental degradations may constitute a brake on growth diminishing life expectancy, and thus savings. It also shows that environmental poverty traps may exist. However,public environmental policies may help countries to escape from such traps, and to reach a higher level of income per capita. In the second chapter, we suggest that the existence of polluting non-renewable resources necessary for production may hamper growth. However, we show that flow pollutions caused by the use of resources can’t be seen as a development brake. Then, following neoclassical works of the1970s, we confirm that exogenous technological progress and sufficient substitution possibilities mayal low to overcome difficulties linked to the exhaustibility of resources. Finally, the third chapter demonstrates that, in low-income economies, strong resource dependency dampens growth while abundanceis growth promoting. Dependence is the outcome of economic choices. Thus a diversification policy that consists on investing the rent in secondary and tertiary sectors may help reduce dependence. Finally, we suggest that the development of education, institutions, and financial markets may allow to decrease the probability to experience a resource curse.

The study of particle morphology plays an important role in understanding the micromechanical behavior of cohesionless soil. Shear strength and liquefaction characteristics of granular soil depend on various morphological characteristics of soil grains such as their particle size, shape and surface texture. Therefore, accurate characterization and quantification of particle shape is necessary to study the effect of grain shape on mechanical behavior of granular assembly. However, the theoretical and practical developments of quantification of particle morphology and its influence on the mechanical response of granular assemblies has been very limited due to the lack of quantitative information about particle geometries, the experimental and numerical difficulties in characterizing and modeling irregular particle morphology. Motivated by the practical relevance of these challenges, this research presents a comprehensive approach to model irregular particle shape accurately both in two and three dimensions. To facilitate the research goal, a variety of natural and processed sand samples is collected from various locations around the world. A series of experimental and analytical studies are performed following the sample collection effort to characterize and quantify particle shapes of various sand samples by using Fourier shape descriptors. As part of the particle shape quantification and modeling, a methodology is developed to determine an optimum sample size for each sand sample used in the analysis. Recently, Discrete Element Method (DEM) has gained attention to model irregular particle morphology in two and three dimensions. In order to generate and reconstruct particle assemblies of highly irregular geometric shapes of a particular sand sample in the DEM environment, the relationship between grain size and shape is explored and no relationship is found between grain size and shape for the sand samples analyzed. A skeletonization algorithm is developed in this study in order to automate the Overlapping Discrete Element Cluster (ODEC) technique for modeling irregular particle shape in two and three dimensions. Finally, the two-dimensional and three-dimensional particle shapes are implemented within discrete element modeling software, PFC2D and PFC3D, to evaluate the influence of grain shape on shear strength behavior of granular soil by using discrete simulation of direct shear test.

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