O uso de filtros polarizadores em óculos de sol está se tornando muito comum em todo o mundo. No Brasil, apesar da norma ABNT NBR15111:2004 ter considerações específicas para seu uso (posição e eficiência), não existe equipamento nacional específico para executar as medidas necessárias para avaliação. Este trabalho descreve o desenvolvimento de um protótipo capaz de executar medidas em óculos de sol para verificar sua adequação à referida norma, que estabelece os seguintes requisitos para os filtros polarizadores: o limite para o desvio entre o eixo de transmissão do filtro polarizador e a vertical é de ±5º e o limite máximo para o desvio mútuo entre os eixos de polarização dos filtros polarizadores das duas lentes é de 6º. Ainda, a eficiência mínima de polarização é de 4:1 para filtros da categoria 1 e de 8:1 para as demais categorias, exceto a categoria 0. O desenvolvimento do protótipo foi dividido em duas etapas: 1. desenvolvimento e avaliação do método de medição, por simulações no software Malab® e testes em bancada; 2. construção do protótipo baseado no projeto, melhorias em bancada e testes preliminares em óculos. O sistema ótico consistiu de: uma fonte de luz (composta por um LED, uma lente biconvexa e um filtro difusor), pelos óculos em teste, pelo filtro analisador (formado por duas metades de filtros polarizadores dispostos com alinhamento perpendicular entre seus eixos de polarização), dois orifícios para passagem de luz designados por pinhole e dois sensores de luz. O sistema eletrônico é composto por seis placas de circuito impresso, a saber: a placa principal onde estão os microcontroladores que executam o software programado; duas placas para controle de motor de passo (filtro analisador e movimento horizontal dos óculos em teste); placa para controle de motor DC (movimento vertical para prender os óculos em teste), placa de alimentação e placa dos sensores. Como resultado, verificou-se a capacidade de posicionamento do filtro analisador com a resolução de 0,08°, a redução do coeficiente de variação de 0,89% para 0,31% pelo uso do filtro difusor, a resolução ótica para medição de um dos óculos de 0,023°, além de um possível problema de alinhamento entre as duas metades que compõe o filtro analisador, o que contribuiu para a desenvolvimento de uma análise mais detalhada das equações de comportamento do protótipo. O protótipo recebeu melhorias nos sistema ótico e eletrônico, além de testes nos óculos de sol disponíveis. No sistema ótico, os sensores foram substituídos por um de maior correlação com a função de sensibilidade para visão diurna V(&#955) e que possui resposta logarítmica, em função disso, o LED do conjunto ótico foi substituído por um de maior potência; também, em função da nova configuração mecânica, a lente da fonte de luz foi substituída por uma biconvexa de diferente distância focal. Assim, a iluminação tornou-se mais homogênea e mais intensa. No sistema eletrônico, utilizou-se um microcontrolador com maior capacidade de processamento, maior memória e conexão USB estável. A interface homem-máquina foi feita por uma tela de cristal líquido sensível ao toque. Os testes com o protótipo foram feitos em quatro óculos de sol polarizados, sendo que, como filtro polarizador de referência para calibração foi utilizada uma das lentes destes óculos. Os resultados preliminares indicaram a viabilidade de se finalizar este sistema como protótipo pronto para uso e calibrá-lo para se obter medidas que proporcionem análises das conformidades da norma brasileira. Contudo, por não ter disponível um filtro calibrador com características apropriadas, os resultados obtidos ainda não podem ser conclusivos. O protótipo construído foi capaz de aplicar o método de medição desenvolvido para caracterizar os óculos de sol, de acordo com as recomendações da norma. Sua estrutura mecânica é robusta e flexível, permitindo o estudo e desenvolvimento de outros métodos de medição e a inserção de outras funções. A contribuição científica e acadêmica deste trabalho reside nos projetos óticos e mecânicos, para se atender a necessidade de construção de um sistema que possa num futuro próximo estar analisando óculos de sol, com as características de um equipamento requerido pela norma brasileira e que não existe no mercado nacional. / The use of polarizing filters in sunglasses is becoming very common worldwide. In Brazil, despite the NBR15111:2004 has specific requirements for its use (position and efficiency), there is no proper national equipment to perform the measurements needed for evaluation. This paper describes the development of a prototype capable to perform measurements on sunglasses in order to verify their suitability for this standard, which establishes the following requirements for polarizing filters: the threshold for the deviation between the transmission axis and the polarizing filter vertical axis is ±5º and the upper limit for the mutual distance between the polarization axis of the two lenses is 6º. The lower efficiency of the polarizing filter is 4:1 for category 1 and 8:1 for all other categories except category 0. The development of the prototype was divided into two stages: 1. Development and evaluation of the measurement method, by software simulations in Malab® and test bench; 2. Prototype construction based on the project, improvements obtained in test bench and preliminary test results with sunglasses. The optical system includes: a light source ( composed by a LED, a biconvex lens and a diffuser filter ), the sunglasses in test, a analyzer filter ( formed by two polarizing filters halves, disposed with their polarization axes perpendicular to each other ), two holes for light transmission (called pinhole) and two light sensors . The electronic system consists of six printed circuit boards , the main board where the microcontroller running software are programmed ; two boards for control of stepper motors (analyzer filter and horizontal movement of the sunglasses in test ); a board to control a DC motor ( vertical motion to hold the sunglasses in test), a power board and a sensor board. As a result of the first step, it was determined the positioning capability of the analyzer filter with a resolution of 0.08°, a reduction of the coefficient of variation from 0.89% to 0.31% by the use of the diffuser, the optical resolution for measuring one of the lenses was 0.023°, also a possible alignment problem between the two analyzer halves, which contributed to the development of a detailed analysis of the behavioral equations of the prototype. The prototype received improvements in optical and electronic systems, and tests with the available sunglasses. In the optical system, the sensors were replaced by a others with higher correlation with the sensitivity function for daytime vision V(&#955) and logarithmic response. As a result, the LED of the light source was replaced by a more powerful one, due to the new mechanical configuration, the lens of the light source was replaced by a biconvex with different focal length, which made the light more homogeneous and intense. The electronic system used a new microcontroller with higher processing power and memory, as well as a more stable USB connection. A man-machine interface was made by including a liquid crystal display, seven-inch touchscreen. Tests with the prototype were made in four polarized sunglasses, the calibration was made using one sunglass lens. Preliminary results indicate the feasibility of this system as complete prototype, ready for use, to obtain measures that provide analyzes in accordance with Brazilian standard. However, by not having available a reference filter with suitable characteristics to serve as a calibrator, the results cannot be conclusive yet. The prototype built was able to apply the measurement method developed for characterizing sunglasses, according to the recommendations of the standard. Its mechanical structure is robust and flexible, allowing the study and development of other methods of measurement and inclusion of other functions. The scientific and academic contribution of this work lies in the optical and mechanical design, to meet the need of building a system that can analyze sunglasses in the near future, with the characteristics required by the Brazilian standard and this equipment does not exist in national market.

<p>The motions of a wavepacket in the two coupled potentials studied in this thesis can be classified into either bistable or astable motion according to the wavepacket interference at the curve crossing. Bistable motion, in which the wavepacket performs a coupled oscillation but remains in the same adiabatic and diabatic state, can exist both in bound-bound systems and bound-unbound ones with long time stability. Astable motion, in which the wavepacket at the curve crossing switches between the adiabatic and diabatic states and thus alternates between the two possible turning points in the unforked part of the motion, can only exist in bound-bound systems on a limited time scale. The motion of a wavepacket under bistable interference conditions exhibits all of the features expected if the wavepacket moved in a single anharmonic potential. The revival time can be predicted from the revival times in the corresponding diabatic and adiabatic potentials. The phenomenon was observed not only in model molecular systems but also in the system of the harmonically trapped ion pumped by an external laser field with standing wave spatial profile.</p><p>In order to study the bias effect of the detector on pump-probe rotational anisotropy measurements, in a specific direction the fluorescence polarization effect was removed by measuring the rovibrational wavepacket with the help of properly oriented polarizer placed in front of the detector. Our results show clearly the necessity to take polarization effects into account in ultrafast pump-probe rotational anisotropy measurements.</p>

The way in which the myocardium responds to its mechanical environment must be understood in order to develop reasonable treatments for congestive heart failure. The first step toward this understanding is to characterize and quantify the cardiac microstructure in healthy and diseased hearts. Myocardium has a laminar architecture made up of myolaminae, which are sheets of myocytes surrounded by a collagen weave. By enhancing the contrast between the myocytes and the surrounding collagen, the myocardium can be investigated and its laminar structure can be quantified. Many of the techniques that have been used to view the microstructure of the heart require the use of toxic or caustic chemicals for fixation or staining. An efficient imaging method that uses polarization microscopy and enhances the contrast between the collagen and myocytes while minimizing the use of harmful chemicals was developed in this research. Collagen is birefringent; therefore its visibility should be enhanced through polarization microscopy and image processing. The sheet angles were viewed directly by cutting slices of a rat septum perpendicular to the fiber angle. Images of different polarization combinations were taken and a region of interest was selected on the sample. Image processing techniques were used to reduce the intensity variation on the images and account for the variable gain of the camera. The contrast between the collagen and myocytes was enhanced by comparing adjusted images to the background and looking at a single image this comparison produced. Although the contrast was enhanced, the embedding media reduced the collagen signal and the enhancement was not as striking as expected.

The motions of a wavepacket in the two coupled potentials studied in this thesis can be classified into either bistable or astable motion according to the wavepacket interference at the curve crossing. Bistable motion, in which the wavepacket performs a coupled oscillation but remains in the same adiabatic and diabatic state, can exist both in bound-bound systems and bound-unbound ones with long time stability. Astable motion, in which the wavepacket at the curve crossing switches between the adiabatic and diabatic states and thus alternates between the two possible turning points in the unforked part of the motion, can only exist in bound-bound systems on a limited time scale. The motion of a wavepacket under bistable interference conditions exhibits all of the features expected if the wavepacket moved in a single anharmonic potential. The revival time can be predicted from the revival times in the corresponding diabatic and adiabatic potentials. The phenomenon was observed not only in model molecular systems but also in the system of the harmonically trapped ion pumped by an external laser field with standing wave spatial profile. In order to study the bias effect of the detector on pump-probe rotational anisotropy measurements, in a specific direction the fluorescence polarization effect was removed by measuring the rovibrational wavepacket with the help of properly oriented polarizer placed in front of the detector. Our results show clearly the necessity to take polarization effects into account in ultrafast pump-probe rotational anisotropy measurements.

Corrosion of reinforced concrete is the most challenging durability problem that threatens reinforced concrete structures, especially structures that are subject to severe environmental conditions (i.e., Highway Bridges, Marine structures, etc.). Corrosion of reinforcing steel leads to cracking and spalling of the concrete cover and billions of dollars are spent every year on repairing such damaged structures. New types of reinforcements have been developed in order to avoid these high cost repairs. Thus it is important to study the corrosion behavior of these new types of reinforcements and compare them to the traditional carbon steel reinforcements.<p> This study aimed at characterizing the corrosion behavior of three competing reinforcing steels; conventional carbon steel, micro-composite steel (MMFX-2) and 316LN stainless steel, through experiments in carbonated and non-carbonated concrete exposed to chloride-laden environments. Synthetic pore water solutions have been used to simulate both cases of sound and carbonated concrete under chloride ions attack. A three electrode corrosion cell is used for determining the corrosion characteristics and rates. Multiple electrochemical techniques were applied using a Gamry PC4 potentiostat manufactured by GAMRY INSTRUMENTS. DC corrosion measurements were applied on samples subjected to fixed chloride concentration in the solution. EIS measurements were applied on samples subjected to incremental chloride additions. Furthermore, carbon steel rebars embedded in concrete samples pre-contaminated with chloride ions added to the mix will be used to relate corrosion rates inside concrete to those obtained from synthetic solutions and to measure moisture content inside concrete using a nondestructive TDR-based technique.

This thesis concerns polarization mode dispersion (PMD) in optical fiber communications. Specifically, we study fiber birefringence, PMD stochastic properties, PMD mitigation and the interaction of fiber birefringence and fiber nonlinearity. Fiber birefringence is the physical origin of polarization mode dispersion. Current models of birefringence in optical fibers assume that the birefringence vector varies randomly either in orientation with a fixed magnitude or simultaneously in both magnitude and direction. These models are applicable only to certain birefringence profiles. For a broader range of birefringence profiles, we propose and investigate four general models in which the stochastically varying amplitude is restricted to a limited range. In addition, mathematical algorithms are introduced for the numerical implementation of these models. To investigate polarization mode dispersion, we first apply these models to single mode fibers. In particular, two existing models and our four more general models are employed for the evolution of optical fiber birefringence with longitudinal distance to analyze, both theoretically and numerically, the behavior of the polarization mode dispersion. We find that while the probability distribution function of the differential group delay (DGD) varies along the fiber length as in existing models, the dependence of the mean DGD on fiber length differs noticeably from earlier predictions. Fiber spinning reduces polarization mode dispersion effects in optical fibers. Since relatively few studies have been performed of the dependence of the reduction factor on the strength of random background birefringence fluctuations, we here apply a general birefringence model to sinusoidal spun fibers. We find that while, as expected, the phase matching condition is not affected by random perturbations, the degree of PMD reduction as well as the probability distribution function of the DGD are both influenced by the random components of the birefringence. Together with other researchers, I have also examined a series of experimentally realizable procedures to compensate for PMD in optical fiber systems. This work demonstrates that a symmetric ordering of compensator elements combined with Taylor and Chebyshev approximations to the transfer matrix for the light polarization in optical fibers can significantly widen the compensation bandwidth. In the last part of the thesis, we applied the Manakov-PMD equation and a general model of fiber birefringence to investigate pulse distortion induced by the interaction of fiber birefringence and fiber nonlinearity. We find that the effect of nonlinearity on the pulse distortion differs markedly with the birefringence profile.

Corrosion of reinforced concrete is the most challenging durability problem that threatens reinforced concrete structures, especially structures that are subject to severe environmental conditions (i.e., Highway Bridges, Marine structures, etc.). Corrosion of reinforcing steel leads to cracking and spalling of the concrete cover and billions of dollars are spent every year on repairing such damaged structures. New types of reinforcements have been developed in order to avoid these high cost repairs. Thus it is important to study the corrosion behavior of these new types of reinforcements and compare them to the traditional carbon steel reinforcements.<p> This study aimed at characterizing the corrosion behavior of three competing reinforcing steels; conventional carbon steel, micro-composite steel (MMFX-2) and 316LN stainless steel, through experiments in carbonated and non-carbonated concrete exposed to chloride-laden environments. Synthetic pore water solutions have been used to simulate both cases of sound and carbonated concrete under chloride ions attack. A three electrode corrosion cell is used for determining the corrosion characteristics and rates. Multiple electrochemical techniques were applied using a Gamry PC4 potentiostat manufactured by GAMRY INSTRUMENTS. DC corrosion measurements were applied on samples subjected to fixed chloride concentration in the solution. EIS measurements were applied on samples subjected to incremental chloride additions. Furthermore, carbon steel rebars embedded in concrete samples pre-contaminated with chloride ions added to the mix will be used to relate corrosion rates inside concrete to those obtained from synthetic solutions and to measure moisture content inside concrete using a nondestructive TDR-based technique.

<p>Geographic clustering has been linked to contemporary political polarization by jour- nalists and other researchers in recent years, most recently and notably by Bishop and Cushing (2008). In these accounts, clustering is motivated, in part, by shared tastes for combinations of place attributes that attract individuals with interrelated values and similar characteristics or skillsets. In order to test whether political pref- erences aligns with location choice, this paper proposes a sorting model based on the composition of migrants' political preferences. </p><p>Sorting is defined as the increase in the variation of a parameter of preference distributions of different location, in the absence of individual preference change. The model estimates the separate prob- abilities of party identification in U.S. congressional districts among migrants and non-migrants.</p><p>Based on an empirical application using the 2006 Cooperative Congressional Elec- tion Study, I find that a significant number of district satisfy the sorting condition. Aa multinomial logit model predicts that individual ideology is significant explana- tory variable in the partisanship of destination districts among migrants, even after controlling for the partisanship of originating districts.</p><p>The final chapter evaluates sorting and polarization in U.S. congressional districts based on intra-decade changes to population size. I show that overall polarization in high growth districts exceeds sorting, and suggest this results from an increase in electoral bias that could result from heavy migration into districts that begin the decade as very homogenous.</p> / Dissertation

Polarization, defined as the ideological distance between the Democrat and Republican parties in Congress, has increased dramatically in Congress since the 1970s. Research on polarization in the U.S. Congress primarily focuses on the sources of this increase. Relatively little work has been done on the consequences of polarization for Congress? relationship with the president and the passage of legislation. This dissertation corrects this omission by examining the influence of polarization on several key aspects of the legislative process. It examines the impact of polarization on the interaction between Congress and the president, including the president?s strategy in supporting or opposing legislation and the success the president has on bills when he takes a position. It also examines the effect polarization has on the overall passage of legislation. An empirical examination was undertaken using significant bills in Congress over a sixty year time period (1947-2006). The results indicate that the effects of polarization on the legislative process are contingent upon the presence of divided government, defined as times when the president and a majority of members of Congress are from different parties, and the chamber of Congress under examination. As polarization increases, the president is more likely to support legislation and be successful when his party controls Congress, but he opposes more legislation and is less successful as polarization increases under divided government. Legislative gridlock, the inability of Congress to pass important or innovative legislation, tends to decrease in both the House and Senate as polarization increases under unified government. However, as polarization increases under divided government the overall passage of bills into law decreases. The dissertation also offers an improved method for modeling the impact of divided government on gridlock. Prior studies model divided government without regard for whether the president takes a position on a given bill. This study shows that when the president takes a position on a bill under divided government the probability it passes decreases, but the probability of passage increases when the president does not take a position. This finding implies that previous research may underestimate the true effects of divided government on gridlock.

Recent days, antennas play an important role in wireless communication system. Microstrip patch antennas are well known to have positive features for cost-effective, low profile and broadband. This type of antenna can be used in wide range of applications such as in wireless communications, radar systems, and satellites. Inhibiting characteristics of single patch antenna with low gain and narrow band leads to the research area to have array configuration. Beam steering antennas are the ideal solution for various systems such as traffic control and collision avoidance radar systems. The goal of this work is to design and implement a dual-linear polarization stacked microstrip patch phased array antenna. Single stacked microstrip patch antenna fed by microstrip line was designed to have approximately 3 GHz bandwidth in X-band with another ground plane to form a stripline-fed. Stripline-fed design protects feed lines from any outside effects. The array configuration was adapted to design in order to accomplish beam scan angle of /- 30 degrees by /- 15 degrees. Binomial power distribution of 3x2 array structure was used in order to reduce grating lobes, and changing length of feed lines was implemented for phase shifting. Bowtie cross shape aperture and dual-offset microstrip feedline was used to feed radiating patches. For the feed network, T-split power divider was implemented and optimized to achieve low loss. The length of microstrip line was adjusted to meet desired phase shift that in wideband application, the length of the line had to be long enough to have similar wavelength response over broad frequency range. The antenna array was designed using standard equations and simulated by electromagnetic analysis software called Zealand's IE3D which is method-of-moments based simulator. The resulting measured impedance bandwidth and gain of both microstrip and stripline-fed single antenna are 43 percent and 5 to 10 dBi with low cross polarizations for all frequencies. The array antenna was measured to have 29 to 60 percent impedance bandwidths depending on the different types of beam scan angles. The gain of the array antenna is 8 to 13 dBi, and the beams are directed as required with /- 3 degrees beam scan angle tolerance. The array antenna had a small offset as compared with simulated results because of the fabrication process such as alignment, distorted feed lines while etching, and etc, but the bandwidths and array patterns were acceptable.