The U.S. social security system faces funding pressure due to the aging of the population. This dissertation examines the welfare cost of social security reform and social security policy uncertainty under rational expectations and under learning. I provide an overview of the U.S. social security system in Chapter I. In Chapter II, I construct an analytically tractable two-period OLG model with capital, social security, and endogenous government debt. I demonstrate the existence of steady states depends on social security parameters. I demonstrate a saddle-node bifurcation of steady states numerically, and demonstrate a transcritical bifurcation analytically. I show that if a proposed social security reform is large enough, or if the probability of reform is high enough, the economy will converge to a steady state. In Chapter III, I develop a three-period lifecycle model. The model is inherently forward looking, which allows for more interesting policy analysis. With three periods, the young worker's saving-consumption decision depends on her expectation of future capital. This forward looking allows analysis of multi-period uncertainty. Analysis in the three-period model suggests that policy uncertainty may have lasting consequences, even after reform is enacted. In Chapter IV, I develop two theories of bounded rationality called life-cycle horizon learning and finite horizon life-cycle learning. In both models, agents use adaptive expectations to forecast future aggregates, such as wages and interest rates. This adaptive learning feature introduces cyclical dynamics along a transition path, which magnify the welfare cost of changes in policy and policy uncertainty. I model policy uncertainty as a stochastic process in which reform takes place in one of two periods as either a benefit cut or a tax increase. I find the welfare cost of this policy uncertainty is less than 0.25% of period consumption in a standard, rational expectations framework. The welfare cost of policy uncertainty is larger in the learning models; the worst-off cohort in the life-cycle horizon learning model would be willing to give up 1.98% of period consumption to avoid policy uncertainty.

Made available in DSpace on 2014-06-11T19:25:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-27Bitstream added on 2014-06-13T19:32:46Z : No. of bitstreams: 1 costa_fb_me_ilha.pdf: 9510999 bytes, checksum: 9a5d3acde99bb0f41fcb579520ce6a76 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os vidros preparados para diversas aplicações têm um ponto em comum: a possibilidade de nuclear e cristalizar novas fases, quando preparados a partir de uma massa fundida ou através de um tratamento térmico acima da temperatura de transição vítrea. Neste trabalho são apresentadas de forma sucinta as formulações teóricas de formação de vidros incidindo principalmente nos processos de nucleação e crescimento de fases. O estudo da cristalização de vidros pode ser feito através de métodos cinéticos baseados na descrição teórica formulada por Johnson-Mehl- Avrami (JMA). Estes métodos descrevem os processos de nucleação e cristalização utilizando dados provenientes das curvas de DTA/DSC. Uma delas é aquela proposta por Kurajica, que determina os parâmetros cinéticos utilizando um modelo para a resolução da sobreposição dos picos de cristalização. Para a aplicação deste modelo, foram utilizados vidros teluretos, de composição 80TeO2 - 10Nb2O5 - 8Li2O - 2V2O5 (mol%) denominados TNLV, e vidros fosfatos, de composição 50P2O5 - 36Na2O - 10CdO - 4La2O3 (mol%), dopados com 20 e 60mg de CeO2 denominados PNCL20 e PNCL60. O estudo cinético teve início com a identificação das fases cristalinas formadas, utilizando a difratometria de raios X (DRX). Considerando a formação de três fases cristalinas para cada sistema vítreo, a equação proposta por Kurajica foi aplicada, utilizando o software Origin 7.0, para determinação dos parâmetros cinéticos, a partir dos ajustes dos dados de DSC. Os coeficientes de Avrami (n) determinados mostraram que para o sistema TNLV o crescimento se dá em três dimensões com mecanismos diferentes, enquanto que para os sistemas PNCL20 e PNCL60, o crescimento ocorre em três dimensões com reação de interface. Foi observado que... / The glasses prepared for various applications have one common point: the possibility of new phases nucleation and crystallization, when prepared from a melt or through a heat treatment above the glass transition temperature. In this work are presented briefly the theoretical formulations of formation of glass focusing mainly in the processes of phases nucleation and growth. The study of glass crystallization can be done by kinetic methods based on the theoretical description formulated by Johnson- Mehl-Avrami (JMA). These methods describe the processes of nucleation and crystallization using data from DTA/DSC curves. One model is that proposed by Kurajica which determine the kinetic parameters resolving overlapping peaks of crystallization. To apply this model were used a tellurite glass, with composition 80TeO2 - 10Nb2O5 - 8Li2O - 2V2O5 (mol%) denominated TNLV, and two phosphate glasses of composition 50P2O5 - 36Na2O - 10CdO - 4La2O3 (mol%) doped with 20 and 60mg of CeO2 denominated PNCL20 and PNCL60. The kinetic study started us with the identification of crystalline phase, using the X-ray diffraction (XRD). Considering that three crystalline phases are formed for each glassy system, the Kurajica equation was applied using the Origin 7.0 software, for determining the kinetic parameters. The calculated Avrami coefficients (n) shown that for the TNLV system the growth occurs in three dimensions with different mechanisms, while for the PNCL20 and PNCL60 systems the growth occurs in three dimensions with an interface reaction. It was observed that the PNCL20 system has higher activation energy that the PNCL60 system and XRD patterns showed that the characteristic peaks of the phases containing CeO2, become higher and thinner in the system PNCL60. These results show that the cerium may favors the glass crystallization.

abstract: A moving overlapping mesh methodology that achieves spectral accuracy in space and up to second-order accuracy in time is developed for solution of unsteady incompressible flow equations in three-dimensional domains. The targeted applications are in aerospace and mechanical engineering domains and involve problems in turbomachinery, rotary aircrafts, wind turbines and others. The methodology is built within the dual-session communication framework initially developed for stationary overlapping meshes. The methodology employs semi-implicit spectral element discretization of equations in each subdomain and explicit treatment of subdomain interfaces with spectrally-accurate spatial interpolation and high-order accurate temporal extrapolation, and requires few, if any, iterations, yet maintains the global accuracy and stability of the underlying flow solver. Mesh movement is enabled through the Arbitrary Lagrangian-Eulerian formulation of the governing equations, which allows for prescription of arbitrary velocity values at discrete mesh points. The stationary and moving overlapping mesh methodologies are thoroughly validated using two- and three-dimensional benchmark problems in laminar and turbulent flows. The spatial and temporal global convergence, for both methods, is documented and is in agreement with the nominal order of accuracy of the underlying solver. Stationary overlapping mesh methodology was validated to assess the influence of long integration times and inflow-outflow global boundary conditions on the performance. In a turbulent benchmark of fully-developed turbulent pipe flow, the turbulent statistics are validated against the available data. Moving overlapping mesh simulations are validated on the problems of two-dimensional oscillating cylinder and a three-dimensional rotating sphere. The aerodynamic forces acting on these moving rigid bodies are determined, and all results are compared with published data. Scaling tests, with both methodologies, show near linear strong scaling, even for moderately large processor counts. The moving overlapping mesh methodology is utilized to investigate the effect of an upstream turbulent wake on a three-dimensional oscillating NACA0012 extruded airfoil. A direct numerical simulation (DNS) at Reynolds Number 44,000 is performed for steady inflow incident upon the airfoil oscillating between angle of attack 5.6 and 25 degrees with reduced frequency k=0.16. Results are contrasted with subsequent DNS of the same oscillating airfoil in a turbulent wake generated by a stationary upstream cylinder. / Dissertation/Thesis / Doctoral Dissertation Aerospace Engineering 2016

The aims of this thesis are to develop and validate a robust and efficient algorithm for the numerical solution of the equations of General Relativistic Hydrodynamics, to implement the algorithm in a computationally efficient manner, and to apply the resulting computer code to the problem of perturbed Bondi-Hoyle-Lyttleton accretion onto a Kerr black hole. The algorithm will also be designed to evolve the space-time metric, and standardised tests will be applied to this aspect of the algorithm. The algorithm will use up-to-date High-Resolution Shock-Capturing numerical schemes that have been developed for the stable and accurate solution of complex systems of equations. It will be built around the Adaptive Mesh Refinement and overlapping, curvilinear grid methodologies in order to extend these schemes to the efficient solution of two and three-dimensional problems. When implementing the algorithm, we will use previously written code libraries, where appropriate, to avoid excessive software development. We will validate the algorithm against standard test-cases for Special and General Relativistic Hydrodynamics, and for Einstein's equations for the evolution of the space-time metric. The methodologies we use will be tested to ensure that they lead to the stable and accurate numerical solution of these problems. Finally, the implemented algorithm will be applied to the problem of Bondi-Hoyle-Lyttleton flow onto a Kerr black hole in three dimensions. It will be validated against existing exact and numerical solutions of the problem, and then be used to perform an extensive parametric study of the problem, varying the spin of the black hole and the incident wind direction, and allowing for the perturbation of the fluid density upstream of the black hole. We will then analyze the results of the study, and present the complete set of results on a DVD accompanying this thesis.

O surgimento de juntas é inevitável em certas construções em concreto armado e para garantir que a estrutura trabalhe de forma monolítica, deve-se proporcionar uma adequada transferência de esforços entre os elementos, para isso, faz-se necessário dispor de uma emenda adequada entre os elementos. Emendas com barras retas ocupam muito espaço devido ao comprimento de traspasse necessário, dessa forma, em situações em que há uma limitação de espaço para a emenda, uma armação que constitui uma boa solução é a emenda por meio de laço, que, apesar de ter poucos estudos relacionados, vem sendo bastante difundida na construção civil. O objetivo desse trabalho é estudar o comportamento de emendas em laço em juntas de estruturas de concreto armado submetidas à tração. Para isso, realizam-se simulações numéricas no software DIANA® em modelos numéricos 3D. Inicialmente, fez-se a calibração do modelo numérico com base em ensaios experimentais da literatura, depois foi realizada uma análise paramétrica variando parâmetros geométricos das peças e da armação em laço. Os resultados mostraram que traspasses menores que o diâmetro de dobra dos laços e espaçamentos maiores que 100 mm se mostram insuficientes para a formação de bielas de compressão entre laços. Dessa forma, ao se utilizar emendas em laço em juntas de concreto armado, recomenda-se dispor as barras o mais próximo possível até um espaçamento máximo de 60 mm entre eixos, como também um traspasse mínimo igual ao diâmetro de dobra dos laços. / The appearance of joints is inevitable in certain constructions of reinforced concrete and aiming to guarantee that the structure works monolithically, it is important to provide an appropriate transfer of stresses between elements, for that, it is necessary using a proper overlapping between them. Straight bars overlappings take up too much space due to the required overlapping length, therefore, in limited space situations, a reinforcement that represents a good solution is the loop joint, which has spread a lot in civil construction, although there are very few studies about it. The aim of the present work is to study the loop joint behaviour in reinforced concrete structures under tension. In order to do so, numerical simulations with numerical 3D models are made using the software DIANA®. Initially, it was made the calibration of the numerical model based on experimental tests of the literature, after that, parametric analyses were performed, varying geometric parameters of the elements and of the loop reinforcement. The results showed that overlapping lengths smaller than the loop diameter and distances between loops axes greater than 100 mm are not sufficient for the development of compression struts between loops. Thus, when the loop joint in reinforced concrete structures is used, it is recommended that the bars are placed as near as possible until a distance between the loops axes of 60 mm and a minimum overlapping length equal to the loop diameter of the reinforcement.

There exists much controversy as to whether international migration in general, and migrant's remittances in particular, increase or decrease economic welfare at origin. Our research contributes to the international discussion on remittances by presenting novel insights on the basis of theoretical and empirical analysis. Analysis of remittances from macro-economic as well as micro-economic point of view reveals that remittances not only have growth enhancing effect but also have an equalizing impact on income distribution of the recipient economy. The first chapter shows how large flows of remittances not only help the receiver to accumulate necessary savings but also reduce the critical level of wealth needed to get access to the capital market to instigate entrepreneurship. The second chapter reveals that the measured impact of remittances on business investment have significant country heterogeneity; remittances facilitate entrepreneurship in those countries where the lenders of the capital market can predict smooth and increasing flow of remittances. The third chapter proposes that remittances work better than aid in enhancing growth of the recipient country and the reason is that remittances are more effective than aid in augmenting capital accumulation.

This thesis contributes to the fields of Public Economics and Development Economics by studying human capital formation under three scenarios. Each scenario is represented in an individual paper between Chapters 2 to 4 of this thesis. Chapter 2 examines the effect of child care financing, through human capital formation, on growth and welfare. There is an extensive literature on the benefits of child care affordability on labour market participation. The overall inference that can be drawn is that the availability and affordability of appropriate child care may enhance parental time spent outside the home in furthering their economic opportunities. In another front, the endogenous growth literature exemplifies the merits of subsidizing human capital in generating growth. Again, other contributions demonstrate the negative implications of taxes on the returns from human capital on long run growth and welfare. This paper assesses the long run welfare implications of child care subsidies financed by proportional income taxes when human capital serves as the engine of growth. More specifically, using an overlapping-generations framework (OLG) with endogenous labour choice, we study the implications of a distortionary wage income tax on growth and welfare. When the revenues from proportional income taxes are channelled towards improving economic opportunities for both work and schooling investments in the form of child care subsidies, long run physical and human capital stock may increase. A higher level of growth may ensue leading to higher welfare. Chapter 3 answers the question of how child care subsidization works in the interest of skill formation, and specifically, whether child care subsidization policies can work to the effect of human capital subsidies. Ample studies have highlighted the significance of early childhood learning through child care in determining the child’s longer-term outcomes. The general conclusion has been that the quality of life for a child, higher earnings during later life, as well as the contributions the child makes to society as an adult can be traced back to exposures during the first few years of life. Early childhood education obtained through child care has been found to play a pivotal role in the human capital base amongst children that can benefit them in the long run. Based on this premise, the paper develops a simple Overlapping Generations Model (OLG) to find out the implications of early learning on future investments in human capital. It is shown that higher costs of child care will reduce skill investments of parents. Also, for some positive child care cost, higher human capital obtained through early childhood education can induce further skill investments amongst individuals with a higher willingness to substitute consumption intertemporally. Finally, intervention that can internalize the intra-generational human capital externalities arising from parental time spent outside the home - for which care/early learning is required to be purchased for the child - can unambiguously lead to higher skill investments by all individuals. Chapter 3 therefore proposes policy intervention, such as child care subsidization, as the effect of such will be akin to a human capital subsidy. The objective of Chapter 4 is to understand the implications of inter-regional mobility on higher educational investments of individuals and to study in detail the impact of mobility on government spending for education under two particular scenarios – one in which human capital externalities are non-localized and spill over to other regions (e.g. in the form of R&D), and another in which the externalities are localized and remain within the region. It is shown that mobility enhances private investments in education, and all else equal, welfare should be higher with increased migration. The impacts on government educational expenditures are studied and some policy implications are drawn. In general, with non-localized externalities, all public expenditures decline under full-migration. Finally under localized externalities, the paper finds that governments will increase their financing of education to increasingly mobile individuals only when agglomeration benefits outweigh congestion costs from increases in regional population.

Dans cette thèse, nous proposons une méthode pour la visualisation d'ensembles chevauchant et de basé sur les diagrammes d'Euler. Les diagrammes d'Euler sont probablement les plus intuitifs pour représenter de manière schématique les ensembles qui partagent des éléments. Cette métaphore visuelle est ainsi un outil puissant en termes de visualisation d'information. Cependant, la génération automatique de ces diagrammes présente encore de nombreux problèmes difficiles. Premièrement, tous les clustering chevauchants ne peuvent pas être dessinées avec les diagrammes d'Euler classiques. Deuxièmement, la plupart des algorithmes existants permettent uniquement de représenter les diagrammes de dimensions modestes. Troisièmement, les besoins des applications réelles requièrent un processus plus fiable et plus rapide.Dans cette thèse, nous décrivons une version étendue des diagrammes d'Euler. Cette extension permet de modéliser l'ensemble des instances de la classe des clustering chevauchants. Nous proposons ensuite un algorithme automatique de génération de cette extension des diagrammes d'Euler. Enfin, nous présentons une implémentation logicielle et des expérimentations de ce nouvel algorithme. / In this thesis, we propose a method for the visualisation of overlapping sets and of fuzzy graph clusterings based on Euler diagrams.Euler diagrams are probably the most intuitive and most used method to depict sets in which elements can be shared. Such a powerful visualisation metaphor could be an invaluable visualisation tool, but the automatic generation of Euler diagrams still presents many challenging problems. First, not all instances can be drawn using standard Euler diagrams. Second, most existing algorithms focus on diagrams of modest dimensions while real-world applications typically features much larger data. Third, the generation process must be reliable and reasonably fast.In this thesis, we describe an extended version of Euler diagrams that can be produced for every input instance. We then propose an automatic procedure for the generation of such diagrams that specifically target large input instances. Finally, we present a software implementation of this method and we describe some output examples generated on real-world data.

Le logiciel, du fait de sa nature particulière, se situe véritablement à la frontière des deux régimes de protection que sont le droit d’auteur et le droit des brevets. C’est pourquoi le logiciel est souvent issu d’une double protection. Il est considéré explicitement en droit iranien et en droit américain à la fois comme une œuvre de l’esprit protégée par le droit d’auteur et comme une invention susceptible d’être brevetée. En droit français, le logiciel est en principe l’objet d’un droit d’auteur spécifique. Pourtant, bien que le législateur ait exclu la possibilité d’une protection de cet objet par le droit des brevets, on constate que les offices du brevet européenne et française délivrent des titres de brevet sur des logiciels. Notre réflexion s’est donc dirigée sur l’articulation de ces régimes de protection- lorsqu’une même création logicielle est à la fois qualifiée d’œuvre de l’esprit protégée par droit d’auteur, et d’invention brevetable. C’est une problématique qui n’a en réalité été que très peu traitée. Le fait d’explorer ce sujet dans les trois ordres juridiques a également conféré à ce travail une certaine spécificité qui a utilement élargi notre réflexion dans nos recherches.Nos axes de réflexion se sont orientés en deux temps : D’abord, nous nous sommes astreints à vérifier si les objets de ces deux régimes de protection étaient identiques ou distinctifs, notamment aux Etats-Unis et en Iran, à savoir dans des pays où la brevetabilité des logiciels est explicitement acceptée par la législation. Ensuite – deuxième temps –, nous nous sommes attachés aux effets de cette distinction des objets vis-à-vis de la titularité des droits – et les prérogatives qui en découlent – et des exceptions au profit du tiers. / Computer program can be protected under both copyright law and patent law under US and Iranian intellectual property law. The European Patent Convention and French intellectual property law explicitly exclude « programs or series of instructions for the procession of operations of a calculating machine », i.e. computer programs from being an patentable subject matter. Despite the non-patentability software, the European and French Patent Offices grant patent qualification without any problems. Because the only protection of computer program by copyright is no longer seen to be sufficient. This expansion has caused overlap to occur between copyright and patent on software.Overlap issues could be arise when an intellectual property rights holder asserts rights under more than one doctrine. That overlapping rights make it difficult for intellectual property users to determine the scope of another’s rights, particularly when those rights have different terms or limitations.Our research begins by defining the components of computer software, followed by an outline of the expansion and overlap of copyright and patent rights. Subsequently, the study will focus on an analysis of the suitability for computer program to be protected by copyright or patent. Ultimately, we will investigate in US and French intellectual property law for the theoretical solutions to this unresolved overlap.

Overlapping genes are adjacent genes that share a portion of their coding sequence. Such genes are often observed in the compact genomes of viruses, prokaryotes,and mitochondria. Overlapping genes are also seen in human and other mammalian genomes. Gene overlapping is a phenomenon to minimize genomic size and maximize encoding capacity. Overlapping genes produce different proteins. A major task in the post genomic era is the large-scale study of the structures and functions of proteins. Proteins play crucial roles in virtually all biological processes. In general it is assumed that 3-D structure determines the function of proteins, but many proteins or region of proteins may function in the absence of 3-D structure. The term disordered is used to describe these proteins. A large number of studies has shown that biological functions depend on both ordered and disordered proteins. Natively disordered regions are common and play essential roles in many proteins, especially, with regard to activities involved in signaling and regulation. The goal of this research was the analysis of the ordered and disordered tendencies of viral proteins encoded by overlapping genes. Our hypothesis is that, in a pair of proteins or protein regions encoded by overlapping genes, at least one of the pair is disordered (or unstructured). Our hypothesis is based on the observation that structural proteins require highly specific amino acid sequences, while unstructured (disordered) sequences are essentially unconstrained. Thus, given a structural protein and its associated mRNA sequence, any sequence derived from an overlapping reading frame seems highly unlikely to have a sequence pattern commensurate with a structural protein; on the other hand, a sequence pattern consistent with a disordered protein seems much more likely. We performed studies on the protein products of overlapping gene sequences, tested the hypothesis and addressed the following two questions: First do the proteins encoded by overlapping genes have opposite order-disorder content, that is, does the ordered part of one of the overlapping proteins correspond to a disordered part in the other overlapping protein? Second, does the encoded protein in the overlapping regions have more disordered amino acids than the non-overlapping regions? Using our database of overlapping viral genes and the protein predictor PONDR VL3, we predicted the order-disorder of amino acids in the sequence of 97 viral protein samples. An analysis of the results supported our hypothesis and indicated that the ordered amino acids are mostly associated with non-overlapping regions while disordered amino acids are more prevalent in overlapping regions. In the overlapping regions for 52 protein pairs, we showed that most of the amino acid pairs facing each other on the protein sequences had at least one disorder for most cases. Out of 52 pairs, there were 3 protein pairs where there were no disordered amino acids and 22 protein pairs where there were no ordered amino acids on either sequence. The fraction of ordered pairs in the pool of overlapping regions of 52 protein pairs was 0.28. The non-overlapping region of 97 proteins had predominantly ordered proteins. The fraction of ordered amino acids in the pool of non-overlapping regions was determined to be 0.77.