Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The use of the quadrature mixing topology has been severely limited in the past due to its sensitivity towards mismatches between its signal paths. In recent years, researchers have suggested that digital techniques can be used to compensate for the impairments in the analogue quadrature mixing front-end. Most authors, however, focus on the modelling and compensation of frequency-independent imbalances, reasoning that this approach is sufficient for narrow band signal operation. This common assumption is, however, becoming increasing less applicable as the use of wider bandwidth signals and multi-channel systems becomes more prevalent. In this dissertation, baseband equivalent distortion models are derived, which model frequency-independent, as well as frequency-dependent contributions towards the imbalances of the front-end. Both lowpass and bandpass imbalances are modelled, which extends current modelling approaches found in literature. The resulting baseband models are shown to be capable of explaining the imbalance characteristics observed in practical quadrature mixing front ends, where existing models fail to do so. The developed imbalance models is then used to develop novel frequency-dependent imbalance extraction and compensation techniques, which directly extract the exact quadrature imbalances of the front end, using simple test tones. The imbalance extraction and compensation procedures are implemented in the digital baseband domain of the transceiver and do not require high computational complexity. The performance of these techniques are subsequently verified through simulations and a practical hardware implementation, yielding significant improvement in the image rejection capabilities of the quadrature mixing transceiver. Finally, a novel, blind imbalance compensation technique is developed. This technique is aimed at extracting frequency-independent I/Q imbalances in systems employing digital modulation schemes. No test tones are employed and the imbalances of the modulator and demodulator are extracted from the second order statistics of the received signal. Simulations are presented to investigate the performance of these techniques under various operating conditions. / AFRIKAANSE OPSOMMING: Die gebruik van die haaksfasige mengtopologie word geweldig beperk deur die sensitiwiteit vir wanbalanse wat mag bestaan tussen die twee analoog seinpaaie. In die afgelope paar jaar het navorsers digitale metodes begin voorstel om te kompenseer vir hierdie wanbalanse in die analooggebied. Meeste navorsers fokus egter op frekwensie-onafhanklike wanbalanse. Hulle staaf hierdie aanslag deur te redineer dat dit ’n aanvaarbare aaname is vir ’n nouband stelsel. Hierdie algemene aanvaarding is egter besig om minder akkuraat te raak, namate wyeband- en multikanaalstelses aan die orde van die dag raak. In hierdie tesis word basisband-ekwiwalente wanbelansmodelle afgelei wat poog om die effek van frekwensie-afhanklike en -onafhanklike wanbalanse akkuraat voor te stel. Beide laagdeurlaat- en banddeurlaatwanbalanse word gemodelleer, wat ‘n uitbreiding is op die huididge modellerings benaderings wat in literatuur gevind word. Dit word aangetoon dat die modelle van hierdie tesis daarin slaag om die karakteristieke van ’n werklike haaksfasige mengstelsel akkuraat te vervat – iets waarin huidige modelle in die literatuur nie slaag nie. Die basisband-ekwiwalente modelle word dan gebruik om nuwe digitale kompensasie metodes te ontwikkel, wat daarin slaag om die frekwensie-afhanklike wanbalanse van die haaksfasige mengstelsel af te skat, en daarvoor te kompenseer in die digitale deel van die stelsel. Hierdie kompensasiemetodes gebruik eenvoudige toetsseine om die wanbalanse af te skat. Die werksverrigting van hiedie kompensasiemetodes word dan ondersoek deur middel van simulasies en ’n praktiese hardeware-implementasie. Die resultate wys daarop dat hierdie metodes daarin slaag om ’n aansienlike verbetering in die beeldonderdrukkingsvermo¨ens van die haaksfasige mengers te weeg te bring. Laastens word daar ook ’n blinde kompensasiemetode ontwikkel, wat gemik is op frekwensie- onafhanklike wanbalanse in digital-modulasie-skama stelsels. Vir hierdie metodes is geen toetsseine nodig om die wanbalanse af te skat nie, en word dit gedoen vanuit die tweede-orde statistiek van die ontvangde sein. Die werksverrigting van hierdie tegnieke word verder bevestig deur middel van simulasies.

La synthèse en une étape de nouveaux matériaux contenant des nanoparticules (NPs) de métal a été réalisée par croissance contrôlée de silices mésoporeuses autour de solutions colloïdales de diverses nanoparticules métalliques (Ru, Pt, Pd, Au). Cette méthodologie a conduit à l’obtention de catalyseurs hétérogènes bien définis (structuration hexagonale 2D du réseau poreux) contenant des NPs régulièrement et sélectivement réparties : au sein des canaux poreux, dans les murs de la charpente silicique ou les deux. Afin d’atteindre ce but, une méthode générale de synthèse en trois étapes a été développée incluant : i) la préparation de la solution colloïdale de nanoparticules hydrophobes ou hydrophiles. ii) la synthèse d’un matériau mésostructuré, autour des NPs, par procédé sol-gel en présence d’un tensioactif structurant, selon un protocole expérimental adapté à la localisation désirée des NPs. iii) décomposition du tensioactif afin de libérer la porosité et la surface des NPs. Les NPs préparées ainsi que les matériaux contenants les NPs ont entièrement été caractérisés par différentes techniques complémentaires (adsorption et désorption d'azote, MET, DRX, WAXS, analyse élémentaire…). Les performances catalytiques, en hydrogénation du propène, déshydrogénation de l’isobutane ou en oxydation de CO, des matériaux ont par ailleurs été comparées à celles d’un catalyseur de référence pour évaluer la stabilité des nanoparticules et les performances catalytiques des nouveaux matériaux ainsi préparés / New materials containing nanoparticles were prepared by the control growth of a mesostructured silica matrix around differents metal colloids (Ru, Pt, Pd, Au). This original methodology led to the selective and regular localisation of small metal nanoparticles in the pores, in the walls, or both in the pores and in the walls of mesostructured silica matrixes. These materials were obtained by: i) the preparation hydrophilic/hydrophobic metal colloids. ii) the growth of silica around these colloids via a solgel process, and using a template. iii) the removal of the surfactant to release the porosity and the NPs surface. The colloidal solutions and the materials were characterised with several techniques such as N2 adsorption/desorption, T.E.M, XRD, WAXS, elemental analysis... Besides, their catalytic performances were tested in propene hydrogenation, isobutane dehydrogenation or CO oxidation and were compared to those of a reference catalyst

Les bactéries du genre Deinococcus sont des microorganismes qui présentent des propriétés remarquables de résistance aux conditions extrêmes telles que les radiations ionisantes, les stress oxydatifs, la dessiccation ou encore les températures extrêmes. L’exploitation de leurs capacités présente donc un réel intérêt pour les procédés biotechnologiques de production de métabolites d’intérêt, les biocarburants. Néanmoins, la physiologie et le métabolisme de ces microorganismes ont été très peu étudiés à ce jour. L’objectif de ce travail est d’identifier les exigences nutritionnelles d’une souche de déinocoques, Deinococcus geothermalis, dans le but de définir la composition d’un milieu synthétique permettant une croissance sans limitation. L’étude statistique de quarante huit formulations de milieux de culture a mis en évidence la variabilité qualitative et quantitative des compositions des milieux utilisés pour leur culture. Il ressort que l’ajout de facteurs stimulant la croissance, sous forme d’extrait de levure, est indispensable à la croissance non limitée de la souche Deinococcus geothermalis DSM 11300. En bioréacteur à 45 °C, sur un milieu complexe et substrat glucose, une concentration finale de 2,7 gMS.L-1 a été obtenue en six heures avec un taux de croissance égal à 0,65 h 1. Les résultats ont montré une variabilité intra-espèce importante ; parmi les trois souches de Deinococcus geothermalis étudiées, DSM 11300, DSM 11301 et DSM 11302, la souche Deinococcus geothermalis DSM 11302 présente la meilleure croissance en termes de nombre de générations, en milieu défini ou complexe. L’étude de l’influence des étapes de préparation de l’inoculum a permis de standardiser les conditions de préparation de l’inoculum préalablement aux cultures en bioréacteur. La souche Deinococcus geothermalis DSM 11302 présente une croissance exponentielle durant quatre heures en bioréacteur sur un milieu défini avec 10 g.L-1 de glucose ; le taux de croissance de 0,25 h-1 ne se maintient pas sur une durée plus longue. Le rendement de production de biomasse à partir du glucose atteint 0,25 gX.gGlc-1 soit 0,30 CmolX.CmolGlc-1. L’ajout de sources carbonées, sources soufrées, vitamines ou autres facteurs de croissance ne permet pas d’améliorer la croissance de la souche dans ces conditions. Sur ces bases, la quantification de la physiologie de Deinococcus geothermalis DSM 11302 a été étudiée lors d’une culture en mode discontinu alimenté avec une stratégie d’apport de deux substrats, l’extrait de levure et le glucose. Le mode de conduite a permis de révéler que le glucose n’est pas la source de carbone assimilée préférentiellement et que l’extrait de levure peut être consommé comme source azotée organique et/ou comme source carbonée. Les déinocoques sont caractérisés par un métabolisme principalement protéolytique : il a été possible de confirmer que l’extrait de levure est indispensable à la croissance non limitée de Deinococcus geothermalis DSM 11302. Avec cette stratégie d’alimentation co-substrats, 253 g d’extrait de levure et 26 g de glucose ont été ajoutés pour produire 99 gMS de biomasse soit 9,6 gMS.L-1 en six heures. Les vitesses spécifiques maximales de consommation des substrats, extrait de levure et glucose, atteignent respectivement 0,68 et 0,39 Cmol.CmolX-1.h-1. Le taux de croissance exponentiel maximal obtenu est égal à 1.05 h-1, meilleur résultat décrit à ce jour pour un déinocoque. Ces résultats contribuent ainsi à implémenter l’état des connaissances sur la physiologie et les exigences nutritionnelles de Deinococcus geothermalis et donnent accès aux valeurs de paramètres cinétiques et de rendements, données absentes de la littérature / Bacteria belonging to Deinococcaceae family are microorganisms with exceptional resistance properties to extreme environmental conditions such as ionizing radiations, oxidative stress, dehydration or extreme temperatures. These properties make them interesting targets for biotechnological processes for metabolite production like biofuels. Nevertheless, physiological behaviour and metabolism of these microorganisms have been little studied to date. The main objective of this work was to study the nutritional requirements for the growth of a Deinococcaceae strain, Deinococcus geothermalis, in order to define a synthetic medium sufficient for a non-limiting growth of this strain. The statistical study of 48 culture media formulations highlighted a lot of variability between the compositions used for their growth. A limiting growth of the strain Deinococcus geothermalis DSM 11300 was obtained on the defined medium DM chosen for this work, in Erlenmeyer flasks and in bioreactor, unless yeast extract was added to the medium. Cultivated in a bioreactor at 45 °C, on a complex medium with glucose (CMG), the biomass concentration reached 2.7 gMS.L-1 in six hours with a growth rate of 0.65 h-1. The results showed intra-specie variability; the strain Deinococcus geothermalis DSM 11302 exhibits the best number of generation in both complex and defined media. The study of the influence of inoculum preparation steps allowed standardizing the conditions of inoculum preparation before cultures in bioreactor. The strain Deinococcus geothermalis DSM 11302 has a four hours exponential growth when cultured in bioreactor on the defined medium DM at 45 °C, but the maximal growth rate of 0.28 h-1 decreases rapidly. The yield of biomass production on glucose reached 0.25 gX.gGlc-1 (0.30 CmolX.CmolGlc-1). Oxygen uptake and glucose specific uptake rates were 3.3 mmol.L-1.h-1 and 0.57 CmolGlc.CmolX.h-1 respectively. None of the carbon sources, sulfur sources or growth factors added to the defined medium DM could improve growth results of the strain Deinococcus geothermalis DSM 11302. For the quantification of Deinococcus geothermalis DSM 11302 physiology, a fed batch culture strategy with a yeast extract and glucose co-substrate feed was chosen. This strategy revealed that glucose is not the preferential carbon source for biomass production. In addition, yeast extract can be consumed as organic nitrogen source and/or as carbon source. Deinococcaceae are mainly proteolytic microorganisms, yeast extract is an essential element to obtain a non-limiting growth of Deinococcus geothermalis DSM 11302. With this co substrate feed strategy, 253 g of yeast extract and 26 g of glucose were added to produce 99 gMS of biomass or 9.6 gMS.L-1 in six hours. The maximal yeast extract and glucose specific uptake rate reached respectively 0.68 and 0.39 Cmol.CmolX 1.h 1. The maximal exponential growth rate is 1.05 h-1, which is the best result describes to date for a Deinococcaceae strain. These results implement the knowledge on physiology and nutritional requirements of Deinococcus geothermalis and give access to quantitative values for characteristic kinetic parameters and conversion yields

Software-Defined Networking (SDN) is a network architecture that differs from traditionalnetwork planes. SDN has tree layers: infrastructure, controller, and application. Thegoal of SDN is to simplify management of larger networks by centralizing control into thecontroller layer instead of having it in the infrastructure. Given the known advantages ofSDN networks, and the flexibility of cloud computing. We are interested if this combinationof SDN and cloud services affects network performance, and what affect the cloud providersphysical location have on the network performance. These points are important whenSDN becomes more popular in enterprise networks. This seems like a logical next step inSDN, centralizing branch networks into one cloud-based SDN controller. These questionswere created with a literature studies and answered with an experimentation method. Theexperiments consist of two network topologies both locally hosted SDN (baseline) and cloudhosted SDN. The topology used Zodiac FX switches and Linux hosts. The following metricswas measured: throughput, latency, jitter, packet loss, and time to add new hosts. Theconclusion is that SDN as a cloud service is possible and does not significantly affect networkperformance. One limitation with this thesis was the hardware, resulting in big fluctuationin throughput and packet loss.

The concept of Software Defined Networking (SDN) may be a way to face the fast growing computer network infrastructure with its demands and requirements. The concept is attracting the interest of enterprises to expand their respective network infrastructures, but one has to consider the impacts of migrating from an existing network infrastructure to an SDN network. One way that could minimize the impacts is to proceed a soft migration from a traditional IP network to SDN, creating what is so called a heterogeneous network. Instead of fully replacing the network infrastructure and face the impacts of it, the idea of the soft migration is to replace a part of it with an environment of SDN and examine the performance of it. This thesis work will analyze the performance of a network consisting of a traditional IP network combined with SDN. It is essential during this work to identify the differences in performance when having a heterogeneous network in comparison with having a dedicated traditional IP network. Therefore, the questions that will be addressed during this thesis work is to examine how such a heterogeneous network can be designed and measure the performance of it in terms of throughput, jitter and packet losses. By the method of experimentation and the studying of related works of the SDN fundamentals, we hope to achieve our goals with this thesis work, to give us and the reader a clearer insight.

Em 1997, o conceito de rádio cognitivo foi proposto pela primeira vez e evoluiu significativamente até os dias de hoje, como solução para o problema da escassez de espectro eletromagnético. Nessa proposta, usuários oportunistas, através de acesso dinâmico ao espectro, fazem uso das faixas de frequências atribuídas a usuários licenciados, quando eles não as estão utilizando. Para que isso seja possível, sem interferir ou degradar os sinais dos usuários licenciados, é necessário atender a quatro requisitos essenciais de rádios cognitivos: Sensoriamento espectral, Decisão do espectro, Compartilhamento do espectro e Mobilidade espectral. Neste trabalho, o sensoriamento espectral é investigado com base na detecção de energia. Um algoritmo é desenvolvido para se determinar o número de canais ocupados e o número de amostras necessárias na detecção para se atingir probabilidades de detecção e falso alarme pré-estabelecidas. Resultados de simulações são apresentadas mostrando que a incerteza do ruído degrada o desempenho do sistema quando a relação sinal-ruído é baixa. O algoritmo desenvolvido permite também determinar o limite inferior para a relação sinal-ruído, quando há incerteza do ruído. O comportamento da probabilidade de detecção em função da probabilidade de falso alarme parametrizado para número de amostras e relação sinal-ruído é apresentado. As curvas resultantes são muitas vezes referidas como curvas ROC - Receiver Operation Characteristics na literatura. Em função do grande interesse sócio-político pela banda de TV, que o cenário das telecomunicações atualmente apresenta, a mesma foi escolhida para alguns exemplos deste estudo. / In 1997, the concept of cognitive radio was proposed for the first time and evolved significantly to the present days, as a solution to the problem of electromagnetic spectrum scarcity. In the proposed approach, opportunistic users utilize frequency bands originally assigned to licensed users through dynamic spectrum access when the licensed users are not using them. To make this possible, without interfering or degrading the signals from the licensed users, it is necessary to fulfill four essential requirements of cognitive radios: spectrum sensing, spectrum decision, spectrum sharing, and spectrum mobility. In this work, spectrum sensing based on energy detection was investigated. An algorithm was developed for the determination of channel occupation and the number of samples needed for the detection process to achieve pre-established probabilities of detection and false-alarm. Simulations results are presented showing that noise uncertainty degrade the performance of the system when the signal-to-noise ratio is low. The developed algorithm allows determining a lower threshold for the signal-to-noise ratio, when noise uncertainty exists. The detection probability behavior as a function of the false alarm probability having the number of samples and the signal-to noise ratio as parameters is presented. The resulting curves are often denominated ROC - Receiver Operation Characteristics in the literature. Due to the high social and political interest in the TV broadcasting band, that telecommunications scenario currently presents, this band was chosen for same examples in this study.

Bien qu'Internet soit considéré comme le grand succès de ces dernières années, il est devenu une infrastructure critique à cause de l'absence de changements dans le réseau cœur et de la rigidité des équipements déployés. La mise en place et le déploiement des nouveaux services réseau sont devenus difficiles et coûteux. La virtualisation des réseaux a été présentée comme un nouveau paradigme pour palier aux problèmes de l’architecture actuelle de l'Internet. Dans ce travail de thèse, nous présentons la virtualisation des réseaux et les réseaux définis par logiciels (SDN) comme solution avec laquelle les fournisseurs de services peuvent offrir, au travers des réseaux virtuels (VN), des nouveaux services aux utilisateurs avec une meilleure qualité de service, tout en optimisant l'utilisation des ressources réseaux physiques. La première contribution consiste à démontrer le potentiel de SDN dans la gestion de la QoS dans le contexte d’un réseau domestique virtualisé. Nous proposons et implémentons le mécanisme ''FlowQoS'' qui peut être déployé par un fournisseur d’accès Internet au niveau de la boucle locale ou bien dans la passerelle domestique. Les mesures des performances montrent que cette solution permet de partager la bande passante entre plusieurs applications selon la configuration définie par l’utilisateur pour garantir la QoS pour chaque trafic actif. La seconde contribution est une modélisation, par la théorie des jeux, de l’interaction entre les fournisseurs de services et les fournisseurs de l’infrastructure pour le partage dynamique de l’infrastructure physique entre plusieurs VN avec différents besoins en QoS. Il s'agit d'un ensemble de jeux non-coopératifs pour modéliser la phase de négociation et celle de l’allocation dynamique des nœuds et des liens physiques pour chaque VN déployé. La troisième contribution porte sur une approche prédictive qui permet d’offrir un contrôle adaptatif de l’allocation de bande passante dans le but de réduire les délais des paquets d'un VN sur chaque lien physique. Ces deux dernières contributions offrent des modèles de partage dynamique des ressources d’une infrastructure physique tout en garantissant la QoS pour chaque VN / Internet has been successful in the recent years. The critical infrastructure of the internet has become stagnant due to the absence of changes in the core networks and stiffness of deployed equipment. It has become difficult and expensive to deploy new network services. Network virtualization is a new paradigm to overcome this problem. In this thesis, we present network virtualization and Software Defined Networking (SDN) as a solution that can be used by service providers. It enables them to provide new services to users through virtual networks (VNs) with better quality of service while optimizing the use of physical network resources. Firstly, we demonstrate the potential of SDN in the QoS management ofa virtualized home network (VN). We propose and implement ''FlowQoS'', a mechanism that can be deployed by an Internet Service Provider in the last-mile hop or in the home gateway. Performance measurements show that this solution can share bandwidth between applications according to user-defined configuration to guarantee QoS for each active traffic. The second contribution is modeling the interaction between service providers and infrastructure providers using game theoretic framework to offer dynamic sharing of physical infrastructure across multiple VN with different QoS requirements. We present a set of non-cooperative games to model the negotiation phase and the dynamic allocation of nodes and physical links for each deployed VN. Finally we focus on a predictive approach that allows an adaptive control of bandwidth allocation in order to reduce the packet delays for a given VN on each physical link. The last two contributions offer dynamic sharing models of physical infrastructure resources while guaranteeing the QoS for each VN

Les réseaux programmables (SDN) sont un paradigme émergent qui promet de résoudre les limitations de l'architecture du réseau conventionnel. Dans cette thèse, nous étudions et explorons deux aspects de la relation entre la cybersécurité et les réseaux programmables. D'une part, nous étudions la sécurité pour les réseaux programmables en effectuant une analyse de leurs vulnérabilités. Une telle analyse de sécurité est un processus crucial pour identifier les failles de sécurité des réseaux programmables et pour mesurer leurs impacts. D'autre part, nous explorons l'apport des réseaux programmables à la sécurité. La thèse conçoit et implémente un pare-feu programmable qui transforme la machine à états finis des protocoles réseaux, en une machine à états équivalente pour les réseaux programmables. En outre, la thèse évalue le pare-feu implémenté avec NetFilter dans les aspects de performances et de résistance aux attaques d’inondation par paquets de synchronisation. De plus, la thèse utilise l'orchestration apportée par les réseaux programmables pour renforcer la politique de sécurité dans le Cloud. Elle propose un Framework pour exprimer, évaluer, négocier et déployer les politiques de pare-feu dans le contexte des réseaux programmables sous forme de service dans le Cloud. / Software Defined Networking (SDN) is an emerging paradigm that promises to resolve the limitations of the conventional network architecture.SDN and cyber security have a reciprocal relationship. In this thesis, we study and explore two aspects of this relationship. On the one hand, we study security for SDN by performing a vulnerability analysis of SDN. Such security analysis is a crucial process in identifying SDN security flaws and in measuring their impacts. It is necessary for improving SDN security and for understanding its weaknesses.On the other hand, we explore SDN for security. Such an aspect of the relationship between SDN and security focusses on the advantages that SDN brings into security.The thesis designs and implements an SDN stateful firewall that transforms the Finite State Machine of network protocols to an SDN Equivalent State Machine. Besides, the thesis evaluates SDN stateful firewall and NetFilter regarding their performance and their resistance to Syn Flooding attacks.Furthermore, the thesis uses SDN orchestration for policy enforcement. It proposes a firewall policy framework to express, assess, negotiate and deploy firewall policies in the context of SDN as a Service in the cloud.

This thesis consists of three self-contained papers on defined benefit (DB) pension provision in the United Kingdom (UK). In particular, in the first paper, I examine the effect that labour market incentives, managerial incentives and the adoption of FRS17 by UK firms, have on DB plan retention decisions. In this paper, I also examine the role of insider trustees, defined as trustees that are also company executives, on the firm’s decision to keep DB plans open. I find that firms for which human capital is especially important are more likely to retain their defined benefit plans. In addition, CEO and CFO membership in the same pension plan that is provided for other employees positively influences the retention of defined benefit pension plans. Additional analysis using a sub-sample for which data on pension plan trustees are available suggests that being a CEO and a trustee increases the probability of DB plan retentions. Moreover, being a CEO/CFO trustee and a member of the DB plan offered to all employees increases the likelihood of DB plan retention. However, I do not find any evidence that voluntary adoption of FRS 17 influences DB plan retention. In addition, I find that insider-trustees have a positive influence on the decision to maintain DB plans, especially when they are members of these plans. In the second paper, I look at the effect of DB plan retentions and executive membership in them, on corporate credit ratings and the investment and dividend decisions. Empirical findings suggest that firms which continue to sponsor DB plans are more likely to have lower credit ratings which are exacerbated when these plans are underfunded. Despite the above effect however, I find that if the CEO is a member of the DB plan, it positively affects credit ratings. In addition, I find some evidence that the participation of CEOs in the main DB plans in conjunction with overfunded pension plans, negatively affect investment decisions when these schemes remain open. I do not find any association between CEOs membership in the main DB plan and dividend payments which may be explained by the market signalling effects of dividends. Finally, in the third paper, I provide a thorough analysis of the pension buy-in and buy-out market in the UK, and I empirically examine the determinants of such transactions from a firm and plan perspective. I find that firms that implement buy-ins have larger and more funded pension plans, are more profitable and have higher union densities. Moreover, firms that complete buy-outs have larger pension plans and allocate less pension assets in equity. Moreover, the number of employees is negatively associated with both transactions implying it is costlier for firms to conduct either a buy-in or buy-out transaction. While union density is positively associated with buy-ins, it has a negative effect on the likelihood of buy-outs suggesting that unions support buy-in but not buy-out transactions. This may be potentially explained by the fact that the latter are associated with with plan winding-ups.

O objetivo deste trabalho é verificar o impacto na alteração do regime previdenciário de repartição para um modelo misto, através da criação do fundo complementar previdenciário para os novos servidores federais no Brasil. O estudo apresenta os diagnósticos e os conceitos e modelos de previdência adotados no Brasil e sintetiza as experiências de países latino-americanos que reformaram seus respectivos regimes previdenciários com a finalidade de reduzir o déficit com os inativos. No caso brasileiro, após a promulgação da Constituição Federal de 1988 foram editadas duas Emendas Constitucionais (a de nº 20 de 1998 e a de nº 41 de 2003) que possibilitaram a criação, em 2012, da entidade fechada de previdência complementar, para os novos servidores públicos federais, chamada FUNPRESP. O estudo conclui que com o surgimento deste fundo, será possível equalizar os valores dos benefícios pagos entre os regimes geral e próprio. Nesse sentido, o teto dos benefícios de aposentadorias pagos do regime próprio dos servidores federais estará indexado ao valor do teto do regime geral de previdência social. Assim, caso o servidor decida suplementar ganhos acima deste teto, para fins de aposentadoria, ele deverá aderir ao fundo e contribuir, sobre o salário participação, em uma conta individualizada. Desta forma, o governo buscou garantir equidade nos pagamentos de benefícios entre os regimes de previdência geral e próprio, além de tentar reduzir o déficit das contas públicas previdenciárias no longo prazo. / The objective of the present paper is to check the impact on changing from the actual social security of federal pensions to a mixed model, through a creation of a defined contribution pension plan for new federal public employees in Brazil. The study show off diagnostics and exhibit the concepts of pension models adopted in Brazil and brief international experiences of countries that have altered their social pension schemes in Latin America, with object to reduce government deficits of inactive. In the Brazilian case, after the Federal Constitution of 1988, Constitutional Amendments were enacted (nº 20 of 1998 and nº 41 of 2003) which enabled the creation, in 2012, of a complementary retirement plan for new federal public employees, called FUNPRESP. The study concludes than with the emergence of this fund, it will be possible to equalize the amounts of benefits paid between pension schemes. Thereby, the remuneration limit of the benefits paid to the actual system of federal employees pensions will be indexed to the remuneration limit of the general social security. Therefore, if the public employee decides complement gains above this compensation limit, for pension purposes, they should choose to contribute with a quota to an individualized pension plan. So, the government tried to ensure equity in benefit payments between the pension schemes, as well as tried to reduce the deficit of the social security public finances in the long term.