Períodos de Fidelização

This dissertation aims to study the loyalty clauses present in most of the long lasting service contracts. We introduce its main features and the consequences that arise from breaching of contract. We analyze the presence of loyalty periods in the Portuguese legislation. In this sense, we discuss Decree-Law 446/85, Law 24/96, Decree-Law 57/2008 and Decree-Law 56/2010. The loyalty period is the minimum period of time for which the contract should be maintained. In most cases, when this obligation is not fulfilled a penalty clause is set, intending to push the weaker party to comply with the contract or sanction it when the party fails to do so. We conclude that the contractual relationship where there is a loyalty period is usually an unbalanced relationship because it only protects the interest of one party. The penalty clause should not be admitted between parties with unequal bargaining powers. The contractual imbalance is not limited to consumer contracts.

Quadrature generators based on ring oscillators and shift registers

Quadrature oscillators are key elements in modern radio frequency (RF) transceivers and very useful nowadays in wireless communications, since they can provide: low quadrature error, low phase-noise, and wide tuning range (useful to cover several bands). RC oscillators can be fully integrated without the need of external components (external high Q-inductors), optimizing area, cost, and power consumption. The conventional structure of ring oscillator offers poor frequency stability and phasenoise, low quality factor (Q), and besides being vulnerable to process, voltage and temperature (PVT) variations, its performance degrades as the frequency of operation increases. This thesis is devoted to quadrature oscillators and presents a detailed comparative study of ring oscillator and shift register (SR) approaches. It is shown that in SRs both phase-noise and phase error are reduced, while ring oscillators have the advantage of occupying less area and less consumption due to the reduced number of components in the circuit. Thus, although ring oscillators are more suitable for biomedical applications, SRs are more appropriate for wireless applications, especially when specification requirements are more stringent and demanding. The first architecture studied consists in a simple CMOS ring oscillator employing an odd number of static single-ended inverters as delay cells. Subsequently, the quadrature 4-stage ring oscillator concept is shown and post-layout simulations are presented. The 3 and 4-phase single-frequency local oscillator (LO) generators employing SRs are presented, the latter with 50% and 25% duty-cycles. The circuits operate at 600 MHz and 900 MHz, and were designed in a 130 nm standard CMOS technology with a voltage supply of 1.2 V.

Switching mode power amplifier for bluetooth applications

Modern fully integrated transceivers architectures, require circuits with low area, low cost, low power, and high efficiency. A key block in modern transceivers is the power amplifier, which is deeply studied in this thesis. First, we study the implementation of a classical Class-A amplifier, describing the basic operation of an RF power amplifier, and analysing the influence of the real models of the reactive components in its operation. Secondly, the Class-E amplifier is deeply studied. The different types of implementations are reviewed and theoretical equations are derived and compared with simulations. There were selected four modes of operation for the Class-E amplifier, in order to perform the implementation of the output stage, and the subsequent comparison of results. This led to the selection of the mode with the best trade-off between efficiency and harmonics distortion, lower power consumption and higher output power. The optimal choice was a parallel circuit containing an inductor with a finite value. To complete the implementation of the PA in switching mode, a driver was implemented. The final block (output stage together with the driver) got 20 % total efficiency (PAE) transmitting 8 dBm output power to a 50 W load with a total harmonic distortion (THD) of 3 % and a total consumption of 28 mW. All implementations are designed using standard 130 nm CMOS technology. The operating frequency is 2.4 GHz and it was considered an 1.2 V DC power supply. The proposed circuit is intended to be used in a Bluetooth transmitter, however, it has a wider range of applications.

Minimal computation structures for visual information applications based on printed electronics

In the early nineties, Mark Weiser wrote a series of seminal papers that introduced the concept of Ubiquitous Computing. According to Weiser, computers require too much attention from the user, drawing his focus from the tasks at hand. Instead of being the centre of attention, computers should be so natural that they would vanish into the human environment. Computers become not only truly pervasive but also effectively invisible and unobtrusive to the user. This requires not only for smaller, cheaper and low power consumption computers, but also for equally convenient display solutions that can be harmoniously integrated into our surroundings. With the advent of Printed Electronics, new ways to link the physical and the digital worlds became available. By combining common printing techniques such as inkjet printing with electro-optical functional inks, it is starting to be possible not only to mass-produce extremely thin, flexible and cost effective electronic circuits but also to introduce electronic functionalities into products where it was previously unavailable. Indeed, Printed Electronics is enabling the creation of novel sensing and display elements for interactive devices, free of form factor. At the same time, the rise in the availability and affordability of digital fabrication technologies, namely of 3D printers, to the average consumer is fostering a new industrial (digital) revolution and the democratisation of innovation. Nowadays, end-users are already able to custom design and manufacture on demand their own physical products, according to their own needs. In the future, they will be able to fabricate interactive digital devices with user-specific form and functionality from the comfort of their homes. This thesis explores how task-specific, low computation, interactive devices capable of presenting dynamic visual information can be created using Printed Electronics technologies, whilst following an approach based on the ideals behind Personal Fabrication. Focus is given on the use of printed electrochromic displays as a medium for delivering dynamic digital information. According to the architecture of the displays, several approaches are highlighted and categorised. Furthermore, a pictorial computation model based on extended cellular automata principles is used to programme dynamic simulation models into matrix-based electrochromic displays. Envisaged applications include the modelling of physical, chemical, biological, and environmental phenomena.

Wideband CMOS low noise amplifiers

Modern fully integrated receiver architectures, require inductorless circuits to achieve their potential low area, low cost, and low power. The low noise amplifier (LNA), which is a key block in such receivers, is investigated in this thesis. LNAs can be either narrowband or wideband. Narrowband LNAs use inductors and have very low noise figure, but they occupy a large area and require a technology with RF options to obtain inductors with high Q. Recently, wideband LNAs with noise and distortion cancelling, with passive loads have been proposed, which can have low NF, but have high power consumption. In this thesis the main goal is to obtain a very low area, low power, and low-cost wideband LNA. First, it is investigated a balun LNA with noise and distortion cancelling with active loads to boost the gain and reduce the noise figure (NF). The circuit is based on a conventional balun LNA with noise and distortion cancellation, using the combination of a common-gate (CG) stage and common-source (CS) stage. Simulation and measurements results, with a 130 nm CMOS technology, show that the gain is enhanced by about 3 dB and the NF is reduced by at least 0.5 dB, with a negligible impact on the circuit linearity (IIP3 is about 0 dBm). The total power dissipation is only 4.8 mW, and the active area is less than 50 x 50 m2 . It is also investigated a balun LNA in which the gain is boosted by using a double feedback structure.We propose to replace the load resistors by active loads, which can be used to implement local feedback loops (in the CG and CS stages). This will boost the gain and reduce the noise figure (NF). Simulation results, with the same 130 nm CMOS technology as above, show that the gain is 24 dB and NF is less than 2.7 dB. The total power dissipation is only 5.4 mW (since no extra blocks are required), leading to a figure-of-merit (FoM) of 3.8 mW

Microstructural changes befor macroeconomic announcements: Predictability of economic surprises in the U.S. market

Flow of new information is what produces price changes, understanding if the market is unbalanced is fundamental to know how much inventory market makers should keep during an important economic release. After identifying which economic indicators impact the S&P and 10 year Treasuries. The Volume Synchronized Probability of Information-Based Trading (VPIN) will be used as a predictability measure. The results point to some predictability power over economic surprises of the VPIN metric, mainly when calculated using the S&P. This finding appears to be supported when analysing depth imbalance before economic releases. Inferior results were achieved when using treasuries. The final aim of this study is to fill the gap between microstructural changes and macroeconomic events.

The determinants of net interest margins & net interest spreads in the Russian & Japanese Commercial Banking sectors

This study presents an empirical investigation of the determinants of net interest margins and spreads in the Russian and Japanese banking sectors with a particular focus on commercial banks. Net interest mar-gins and spreads serve as indicators of financial intermediation efficiency. This paper employed a bank-level unbalanced panel dataset prolonging from 2005 to 2014. My main empirical results show that bank characteristics explain the most of the variation in not only net interest margins but also in spreads. Capi-talization, liquidity risk, inflation, economic growth, private and government debt are important determi-nants of margin in Russia. In Japan to the contrary loan and deposit market concentration along with bank size do predominate. Common significant variables in both countries are the substitution effect, cost effi-ciency and profitability. Turning to net interest spreads, micro- and macro-specific variables are the main significant drivers in Russia. I reach the conclusion that there are no significant determinants of net interest spreads in Japan within the original selection of variables, but operating efficiency and deposits to total funding seem to prevail. In both countries, there are solid differences in the net interest margins as well as spreads once the pre- and the post-crisis periods are considered.

As Comissões Parlamentares de Inquérito no Portugal democrático, 1976-2015

As transformações operadas no mundo contemporâneo, em especial no que respeita às estruturas do poder, à sua maior autonomização e diferenciação, tiveram particulares reflexos ao nível dos Parlamentos e das funções que prosseguem. Desde a sua origem, no passado século XIII, à atualidade, grandes acontecimentos, clivagens e factos históricos estão presentes na sua linha evolutiva. A democratização do regime parlamentar e a legitimidade outorgada através de eleições democráticas e concorrenciais são um marco ímpar na sua história. A complexidade das sociedades hodiernas catapultou o Poder Executivo em detrimento do Parlamento, enquanto órgão legislativo por excelência. Tal circunstancialismo levou, não ao proclamado declínio dos Parlamentos, mas a reformas estruturantes. Outras e mais importantes funções seriam prosseguidas. Se as iniciativas legislativas e a definição das políticas públicas passaram a ser quase um exclusivo do Governo, havia que desenvolver e ampliar, por parte dos Parlamentos, os instrumentos de controlo, fiscalização e escrutínio da ação governativa. Entre os clássicos instrumentos de controlo avulta o Inquérito Parlamentar, materializado em Comissões Parlamentares de Inquérito, dotadas de poderes especiais para recolha de informação e para investigação. No seu percurso parlamentar, também as Comissões de Inquérito foram sendo alvo de constantes aperfeiçoamentos, de ordem constitucional, legal e regimental. A excessiva partidarização da atividade parlamentar de outrora e sobretudo a confusão entre o governo e o partido que o sustentava a nível parlamentar, o confronto desequilibrado de meios entre as maiorias e as minorias, levaram a um reposicionamento do inquérito parlamentar enquanto garante do direito das minorias. Não sendo expectável que as grandes iniciativas de controlo sejam tomadas pelo partido maioritário, cabe à oposição esse papel. Em Portugal, diminuta era a tradição do instituto do inquérito parlamentar, razão porque foi efémera e sem resultado a sua utilização no tempo da monarquia constitucional. O regime democrático, abraçado com o 25 de abril de 1974, relançou o órgão de soberania Parlamento e estabeleceu prioridades. Até ao amadurecimento da democracia viveram-se tempos mais conturbados mas de grande aprendizagem. O inquérito Parlamentar, a partir da revisão constitucional de 1982, passou conceptualmente a integrar um dos meios mais relevantes da fiscalização política. É, pois, o levantamento exaustivo e a análise das Comissões Parlamentares de Inquérito no Portugal democrático, período de 1976-2015, o objetivo a que nos propomos neste estudo.