Este trabalho consiste no estudo dos fatores envolvidos no projeto estrutural de pontes, mais especificamente aqueles relacionados com o comportamento dos seus pilares. A análise é efetuada mediante uma modelagem única da estrutura integrada ao maciço de solos, onde as não-linearidades física e geométricas e interação solo-estrutura são consideradas. Inicialmente é feita uma abordagem sobre a concepção do projeto dos pilares e seus arranjos, destacando os problemas diretamente envolvidos no seu cálculo. É apresentada uma formulação simples, baseada em uma só fibra ativa, para levar em consideração a não linearidade física do concreto armado. A não-linearidade geométrica é tratada quanto aos seus aspectos e critérios de utilização, e também é apresentada uma formulação baseada na Energia Potencial Total para a obtenção da matriz de rigidez tangente da estrutura. O maciço de solos é modelado com dispositivos discretos parametrizados através de curvas de resistência lateral p-y. Os aparelhos de apoio são modelados através de elementos de contato devidamente parametrizados. Finalmente, são incluídos alguns exemplos numéricos de casos típicos de pontes / This work deals with the study of factories involved in bridge structural design, specifically in regards with column behavior. The analysis is made by a unique model integrated in the soil massy, where the geometric and physics non-linearity and soil-structure interactions are taken into account. At first, it is made an approach about criteria and details of bridge column design. It is showed a simple formulation; based in one unique active fiber discretization, to consider the physics non-linearity of reinforced concrete Main aspects of geometrical non-linearity are presented. Also it is showed a formulation based in Total Potential Energy in order to obtain the structure tangent stuffiness matrix. The soil massy is modeled with discrete mechanisms by p-y lateral resistance curves. The bearing cushion pads are modeled by contact elements. At end, they are included some numerical examples of bridge typical structures

La mécanique quantique est sans aucun doute la théorie la mieux vérifiée qui n’a jamais existée. En se retournant vers le passé, nous constatons qu’un siècle de théorie quantique a non seulement changé la perception que nous avons de l’univers dans lequel nous vivons mais aussi est responsable de plusieurs concepts technologiques qui ont le potentiel de révolutionner notre monde. La présente dissertation a pour but de mettre en avance ces potentiels, tant dans le domaine théorique qu’expérimental. Plus précisément, dans un premier temps, nous étudierons des protocoles de communication quantique et démontrerons que ces protocoles offrent des avantages de sécurité qui n’ont pas d’égaux en communication classique. Dans un deuxième temps nous étudierons trois problèmes spécifiques en clonage quantique ou chaque solution apportée pourrait, à sa façon, être exploitée dans un problème de communication quantique. Nous débuterons par décrire de façon théorique le premier protocole de communication quantique qui a pour but la distribution d’une clé secrète entre deux parties éloignées. Ce chapitre nous permettra d’introduire plusieurs concepts et outils théoriques qui seront nécessaires dans les chapitres successifs. Le chapitre suivant servira aussi d’introduction, mais cette fois-ci penché plutôt vers le côté expériemental. Nous présenterons une élégante technique qui nous permettra d’implémenter des protocoles de communication quantique de façon simple. Nous décrirons ensuite des expériences originales de communication quantique basées sur cette technique. Plus précisément, nous introduirons le concept de filtration d’erreur et utiliserons cette technique afin d’implémenter une distribution de clé quantique bruyante qui ne pourrait pas être sécurisé sans cette technique. Nous démontrerons ensuite des expériences implémentant le tirage au sort quantique et d’identification quantique. Dans un deuxième temps nous étudierons des problèmes de clonage quantique basé sur le formalisme introduit dans le chapitre d’introduction. Puisqu’il ne sera pas toujours possible de prouver l’optimalité de nos solutions, nous introduirons une technique numérique qui nous permettra de mettre en valeur nos résultats.

[pt] Esta dissertação apresenta um desenvolvimento analítico que permite caracterizar as distorções produzidas na densidade espectral de potência de sinais OFDM devido à sua passagem através de sistemas não lineares. O processo estocástico que caracteriza a envoltória complexa de um sinal OFDM é odelado como um processo estocástico gaussiano complexo, próprio. A não linearidade do canal de transmissão é caracterizada pela expansão, em série de potências, de suas características de conversão AM/AM e AM/PM. Utilizando-se o Teorema dos Momentos para processos gaussianos complexos chega-se a expressões analíticas fechadas para a função autocorrelação e para a densidade espectral de potência do sinal produzido na saída da não- linearidade. As expressões obtidas são aplicadas a situações particulares nas quais 1, 2 e 3 sinais OFDM compartilham a não- linearidade permitindo quantificar, nestas situações específicas, as distorções correspondentes aos produtos de intermodulação de diferentes ordens e o efeito, nestas distorções, de variações no valor do back-off de entrada do sinal. / [en] This MSc dissertation presents a theoretical analysis that evaluates the distortion experienced by the power spectrum density of OFDM signals when they are transmitted through a non-linear channel. The complex envelope of the OFDM signals are modeled as a complex proper gaussian random process and the channel non-linearity is characterized through a power series expansion of its AM/AM and AM/PM distortion curves. Using the Moment Theorem for complex gaussian random processes, closed form expressions for the autocorrelation function and the power spectrum density of the signal produced at the non-linear channel output are obtained. These expressions are applied to specific situations in which 1, 2 and 3 OFDM signals share the nonlinear channel, producing results that quantify the distortions corresponding to intermodulation products of different orders and the effect of varying the signal input back-off value.

This thesis documents the design and analysis of a low-power integrated ultra-wideband (UWB) receiver that is well suited for usage in medium to low rate, location aware communication systems. For the first time, this receiver design explores and exploits the unique properties of UWB pulse technology. By exploiting low emission power limit and pulse based communication, RF circuits have been designed with reduced linearity to achieve low-power operation and better circuit performance. The receiver design in this thesis follows a top-down approach which begins by focusing on UWB-specific issues such as signal characteristics, modulation schemes, potential advantages, and design challenges. Next, different receiver architectures are evaluated in terms of their circuit complexity, power consumption, and levels of integration. The impact of various analog non-idealities on the performance of UWB systems is also analysed in detail. After evaluating the performance of UWB systems operating with non-linear frontends, the use of pulse doublets is introduced, for the first time, to mitigate nonlinearityinduced distortion. Simulation results demonstrate that under non-linear operating conditions, significant BER improvements can be achieved by using filtering, pulse doublet, and direct sequence spread spectrum techniques. When ADC quantization effects are included in the receiver, analysis shows that quantization noise dominates distortion-induced BER degradation when two or three bits ADCs are employed. Consequently, reduced front-end linearity requirements can be tolerated in exchange for improvements in the more critical circuit parameters of the UWB receiver. By adopting the sub-linear circuit design approach, a direct-conversion receiver prototype is implemented in the 0.5 um SOS CMOS technology according to specifications determined from system-level Simulink simulations. This highly integrated receiver prototype contains a low-noise amplifier, a 4-GHz frequency synthesizer, mixers, baseband amplifiers and filters, and 2-GSps two-bit analog-to-digital converters. The receiver prototype consumes 75-mW of power, the lowest amount for reported UWB receivers operating in the 3.1 to 10.6-GHz band. Complete end-to-end simulations of the system are performed in Simulink, revealing an achievable BER of approximately 8x10e-4 Finally, a novel 79-uW 5.6-GHz CMOS frequency divider with on-chip temperature and processing compensation have been designed. The divider, designed in a 0.25 um SOS-CMOS technology, occupies 35 x 25 um2 and achieves an operating frequency of 5.6-GHz while consuming 79-uW at a supply voltage of 0.8V. The power efficiency of 143-GHz/mW is one of the highest achieved among conventional CMOS dividers. When combined with a simple and effective compensation submodule, the proposed divider is shown to achieve process and temperature-insensitive operation in a 5-GHz UNII band frequency synthesizer.

<p>In this paper, we study the industrial production index of Sweden from Jan, 2000 to latest Feb, 2010. We find out there is a structural break at time point Dec, 2007, when the global financial crisis burst out first in U.S then spread to Europe. To model the industrial production index, one of the business cycle indicators which may behave nonlinear feature suggests utilizing a smooth transition autoregressive (STAR) model. Following the procedures given by Teräsvirta (1994), we carry out the linearity test against the STAR model, determine the delay parameter and choose between the LSTAR model and the ESTAR model. The results from the estimated model suggest the STAR model is better performing than the linear autoregressive model.</p>

The IEEE 802.11a has become the mainstream protocol used in modern wireless communication system due to its high propagation rate of data (54 Mb/s). To meet high propagation rates, the communication devices used in IEEE 802.11a protocol usually present a high conversion gain and a high linearity (denoted as third order intercept point, IIP3). The IIP3 of conventional up- and down-conversion mixers are only about 0 dBm and -5 dBm, which fail to achieve a high propagation rate of data. This thesis utilizes the TSMC 0.18 &#x00B5;m CMOS technology to design and fabrication up- and down-conversion mixers with very high linearity for IEEE 802.11a application. The proposed high-linearity up-conversion mixer with 1.01 mm ¡Ñ 0.85 mm chip size and its wide bandwidth (5~6 GHz) is well suited for IEEE 802.11a application. To enhance the linearity and bandwidth, a transconductor stage with gm-boosted structure, a switch stgae with LO-body grounded structure and a load stage with shunt peaking structure are adopted in this research. Under 5.2/5.4/5.8 GHz operating frequencies, the implemented up-conversion mixer demonstrates a high conversion gain of 6.8/7.1/6.3 dB and a high linearity of 8.9/9/13.2 dBm, respectivly. In addition, a moderate consuming power (6.86 mW) of such mixer can be achieved at 1.2 V supply voltage. On the other hand, this thesis also designed and fabricated a high-linearity down-conversion mixer with chip size of 1.02 mm ¡Ñ 0.86 mm and 5.2 GHz center frequency. To improve the linearity and isolation and reduce the high-order noise, a transconductor stage with dual-gate structure and a load stage with RC-tank structure are adopted in this research. According to the EM-simulation resutls, the proposed down-conversion mixer presents a moderate conversion gain of 6 dB and a high linearity of 0.8 dBm. Additionly, a moderate consuming power (6.75 mW) of such mixer can be achieved at 1.8 V supply voltage.

In this paper, we study the industrial production index of Sweden from Jan, 2000 to latest Feb, 2010. We find out there is a structural break at time point Dec, 2007, when the global financial crisis burst out first in U.S then spread to Europe. To model the industrial production index, one of the business cycle indicators which may behave nonlinear feature suggests utilizing a smooth transition autoregressive (STAR) model. Following the procedures given by Teräsvirta (1994), we carry out the linearity test against the STAR model, determine the delay parameter and choose between the LSTAR model and the ESTAR model. The results from the estimated model suggest the STAR model is better performing than the linear autoregressive model.

The trade-off between linearity and efficiency is the key limiting factor to wideband power amplifier design. Current wireless research focuses much of its effort on building power amplifiers with the two aforementioned criteria going hand in hand to build an optimal design. This thesis investigates the sources of nonlinearity associated with GaN high electron mobility transistors (HEMT), and their subsequent effects on the linearity metrics of the power amplifier. The investigation began with an analysis of the sources of nonlinearity, and then a design-based approach to mitigate those sources of nonlinearity was developed. This design approach was compared with existing trends in power amplifier design. The device technology used in the design was CREE GaN HEMT (45W and 6W). In this report, a systematic approach to designing a two stage power amplifier is discussed, and analyzed for design of linear and highly efficient power amplifiers for base stations. The designed power amplifier consists of two stages: a driver stage and a power stage. The driver stage aimed to linearize the power stage by using circuit analysis and transistor properties along with providing the necessary gain. The power stage was built to complement the driver stage and to achieve high efficiency for the power amplifier. An inter-stage matching network placed between the two stages allowed for the required matching of impedances; transmission lines in the bias feed controlled the harmonic impedances for optimal performance without disrupting performance at fundamental frequencies. This approach effectively improved, and maintained, high efficiency over 200MHz of bandwidth. The design approach was simulated and fabricated in order to test the feasibility of linear power amplifier operation with the use of digital pre-distortion (DPD). The fabricated prototype achieved about 70% peak efficiency over the bandwidth and maintained linearity above 40dBc adjacent channel leakage ratio (ACLR) and below 3% error vector magnitude (EVM). The measurement results indicated that the need for DPD was eliminated when the power amplifier was operating in back-off at the center frequency (800MHz). This thesis compares the prototyped design with existing multistage designs which use linear drivers. The report provides conclusions derive from measurement results and bandwidth limitations faced throughout the course of the design. Lastly, potential research directions, which may allow researchers to overcome the limitations of this design, are discussed.

This dissertation consists of two parts. The theme connecting the two parts is the role of uncertainty. The first part focuses on the role of uncertainty in cooperative bargaining and public decision making. I provide an axiomatic characterization of the normalized utilitarian solution to bargaining problems involving uncertainty. In addition to three basic axioms that are common in the bargaining literature, I propose the axiom of weak linearity to characterize the solution. In the second part I study uncertainty in non-cooperative games by designing a principal agent model of public bailouts. The first essay in this part sets up the model and shows that the moral hazard problem, namely the Samaritan's dilemma, exists without an altruistic principal. The second essay in this part builds upon the previous essay and focuses on the informational elements in a bailout game. Mainly, I show the existence of a separating equilibrium, where public bailouts serve as a mechanism to reveal essential information to outsiders and in which the good-type agents can benefit from rejecting a bailout offer.

The variable gain amplifier (VGA) is utilized in various applications of remote sensing and communication equipments. Applications of the variable gain amplifier (VGA) include radar, ultrasound, wireless communication and even speech analysis. These applications use the variable gain amplifier (VGA) to enhance dynamic performance. The purpose of the thesis work is to implement a high linearity and low noise variable gain amplifier in 150 nm CMOS technology, for an analog-front-end of a transceiver. Two different amplifier architectures are designed and compared. First architecture is an amplifier with diode connected load and second architecture is a source degenerative amplifier. The performance of the amplifier with diode connected load is lower than the source degenerative amplifier in terms of gain, power, linearity, noise and bandwidth. So, the source degenerative amplifier is selected for implementation. The three stage variable gain differential amplifier is implemented with selected architecture. The implemented three stage variable gain differential amplifier have gain range of -541.5 mdB to 22.46 dB with step size of approximately 0.3 dB and total gain steps are 78. The -3 dB bandwidth achieved is 953.3 MHz. The third harmonic distortion (HD3) is -45 dBc at 250 mV and the power is 35 mW at 1.8 V supply source.