Many commercial and laboratory applications of fiber optics require an ability to manipulate, change and control the state of polarization of light. This is usually accomplished with bulk-optic wave plates which are inherently narrowband, bulky, and often require careful manual tuning and adjustments. H.C. Huang has recently proposed that a variably spun birefringent fiber with spin rate slowly varying from zero to very fast (or vice versa) will transform the state of polarization (SOP) from linear to circular (and vice versa). The most remarkable feature of a Huang fiber is that the transformation from linear to circular polarization is independent of wavelength over entire single mode range of the fiber. In this thesis, using simulations and experiments we explore the properties of such a fiber element and investigate its similarities and differences as compared to a bulk-optic quarter-wave plate. In the simulations, we modeled the Huang fiber as a stack of birefringent waveplates and used this model verify the theoretically predicted polarization transformation behavior and the wideband nature of the Huang fiber. We analyzed the dependence of the polarization transformation by this device on various structural parameters and showed that while the fiber has loose tolerances with respect to the fiber length and the spin variation, it has a strong dependence on the maximum spin rate at the high-spun end. We investigated the PMD characteristics of the Huang fiber for short pulse applications. Using simulations we also verified that two such quarter wave-transforming fibers can be appropriately cascaded to obtain half-wave and full-wave transformation, analogous to bulk optics half wave and full wave plate respectively. In the experiments we studied the polarization transformation behavior of a Huang fiber sample when it is excited by different input states of polarization both from the un-spun end and the high-spun end. We found that the results from the experiments strongly support the simulation results. The experiment was performed at 1310 nm and 1550 nm to verify the wideband nature of the Huang fiber sample. We found that the Huang fiber indeed performs the prescribed state of polarization transformation over a wide band. / Master of Science

The survivability of U.S. warships has become a higher priority than ever before. Two ways to improve survivability are to either avoid damage, or to continue to operate after damage has been incurred. This thesis concentrates on the first line of defense, which involves the first of these two approaches. Specifically, this thesis evaluates the extent of threat due to optical contrast with the ocean background. As part of this effort, an MCRT tool was created that allows the user to vary the shape and surface properties of a ship. A reverse MCRT was performed in order to reduce the processing time required to get accurate results. Using this MCRT tool, the user can determine the theoretical contrast with the ocean surface that would be seen at any viewing angle with and without a polarization filter. The contrast due to differential polarization and a change in viewing angle is estimated to determine the extent of threat. These results can be determined for both daytime and nighttime conditions by specifying if the ray trace is in the infrared or visible light range. The location of the sun for daytime conditions, and the temperature of the surfaces for nighttime conditions, can all be adjusted by the user. In order to get an accurate estimation of the signal power coming from the ocean surface, a great deal of time and effort was spent modeling the ocean surface. Many studies have been done concerning the slope statistics of an ocean surface, some more informative than others. This thesis takes two of the most complete studies and brings them together to get accurate slope statistics in both along-wind and crosswind directions. An original idea by the author was used to give a typical shape to the waves of the simulated ocean surface. The surface properties of the ship were determined using Fresnel's equations and the complex index of refraction of water at the particular wavelengths of interest. / Master of Science

Master of Science

Much attention has been paid to the growing level of polarization at both the party level and within the American public, particularly since the late 1970's. Many scholars will either argue that elite polarization is representative of pre-existing, strongly felt political beliefs in the electorate, or that voters act on the basis of the elite cues they observe in politicians. Scholarship has been lacking, however, a microlevel analysis of the polarization of elite discourse, its motivations, and its effects on the American voter. This study quantifies the divergence in party discourse on particular issues through an analysis of published platforms and presidential candidate convention speeches. By employing Foucauldian theories of micropolitics and biopower, a qualitative case study, critical discourse analyses, and ANES polling data, this study finds that not only have the parties been deploying drastically diverging discourses on issues of biopolitical administration, but this also tends to engender political saliency on issues in which voters were not significantly concerned. There are certainly insidious implications for a representative system of government when parties utilize discourse to manufacture political opinions for their own self-interest. The data herein show that both parties have been guilty of such mobilization tactics within the last forty years. / Master of Arts / Even the most casual observer of the American political system will note the adversarial and polarized relationship between Republicans and Democrats. Rather than focusing on the general differences between the two parties, this project looks at how the language and dialogue of political elites affects the average American voter. What I found is that, as the two parties discussed certain issues more frequently and in distinct ways, these issues became increasingly important to the American electorate. In other words, politicians tell voters which issues are important to them through their choice of rhetoric. This is quite different than common assumptions of democratic societies where legislators merely represent the interests of their constituents, rather than manufacture them.

A flow solid/liquid intermolecular transfer (SLIT) ¹H dynamic nuclear polarization (DNP) experiment is described. The SLIT ¹H DNP results are reported for the case of flowing benzene over silica gel surfaces prepared with stable immobilized nitroxide and phenoxy spin labels. The advantages of the flow SLIT DNP experiment in comparison with the recently reported flow liquid/liquid intermolecular transfer (LLIT) ¹H DNP experiment are discussed. The results suggest that the flow SLIT DNP experiment provides a new method for monitoring liquid/surface intermolecular interactions, since the reporter group (flowing benzene) reflects properties of the surface. Potential applications such as: 1) observation of enhanced NMR signals without detrimental line broadening due to the presence of stable free radicals in the NMR detection region, and 2) independent optimization of the "EPR" and "NMR" portions of the DNP experiment, are discussed. The thrust of this thesis was twofold: 1) to synthesize immobilized free radical systems appropriate for the SLIT DNP measurements, and 2) to establish the factors influencing DNP mechanism(s) for these systems. The resulting ¹H DNP line shapes imply that both Overhauser effect and solid- state effect are effective mechanisms for the DNP enhancements. The results suggest that the relatively low magnitude of the enhancements can be attributed to the longer molecular correlation times of the solid/liquid systems studied. Also, the EPR spectra and the corresponding number of unpaired spins were measured for these immobilized systems. / M.S.

Yes / The antenna presented in this study is a compact wideband monopole with wideband circular polarization that can be used across the whole antenna bandwidth. A rectangular C-shaped patch is partially covered by a ground plane in the proposed planar monopole antenna. Inserting a rectangular stub to the ground plane, etching a slit at the antenna patch, and adding a semicircular stub at the top of the antenna feed line increase the antenna impedance bandwidth (BW) and axial ratio bandwidth (ARBW). An FR4 substrate with overall dimensions of 25 mm×25 mm×1.6 mm is used to create the antenna. The antenna's observed impedance BW is 70% (4.55 GHz in the 4.3-8.85 GHz band), while the measured broadside ARBW is improved to a value of 82.2 percent (5.3 GHz along the range 3.8-9.1 GHz). The impedance BW is perfectly covered by the ARBW; hence the antenna can be considered circularly polarized throughout its operational spectrum. Within the antenna BW, the measured gain is greater than 1.5 dB.

No description available.

Vacuum polarization by electric fields is a well established fact. Assuming that anti-matter has negative gravitational properties, the fluctating electric dipoles from the quantum vacuum may also have gravitational dipolar properties. A model is developed that describes how electric fields could gravitationally polarize the vacuum causing gravitational screening or anti-screening effects. This leads to a violation of the Weak Equivalence Principle or a general mass change most notabily for elementary particles, such as the electron or positron, below but close to measured boundaries. Also a gravitational vacuum torque is predicted to act on a charged capacitor perpendicular to a gravitational field. The predictions could be verified by future laboratory experiments that could contribute on our understanding of the gravitational properties of anti-matter.

Azimuthal anisotropy, assumed to be associated with vertical, aligned cracks, fractures, and subsurface stress regimes, causes vertically propagating shear waves to split into a fast component, with particle motion polarized parallel to fracture strike, and a slow component, with particle motion polarized perpendicular to fracture strike. Determining the polarization of each split shear wave and the time lag between them provides valuable insight regarding fracture azimuth and intensity. However, analysis of shear wave polarizations in seismic data is hampered by reflection-induced polarization distortion. Traditional polarization analysis methods are limited to zero offset and are not valid if implemented over the full range of offsets available in typical 3D seismic data sets. Recent proposals for normalizing amplitudes recorded at non-normal incidence to values recorded at normal incidence may provide an extension to correcting offset-dependent shear wave polarization distortion. Removing polarization distortion from shear wave reflections allows a larger range of offsets to be used when determining shear wave polarizations. Additional complexities arise, however, if fracture orientation changes with depth. Reflections from layers with different fracture orientations retain significant energy on off-diagonal components after initial rotations are applied. To properly analyze depth-variant azimuthal anisotropy, time lags associated with each interval of constant anisotropy are removed and additional iterative rotations applied to subsequent offset-normalized reflections. Synthetic data is used to evaluate the success of these methods, which depends largely on the accuracy of AVA approximations used in the correction. The polarization correction effectively removes SV polarity reversals but may be limited in corrections to SH polarizations at very far offsets. After the polarization correction is applied, energy calculations including incidence angles up to 20° more effectively compensates individual SV and SH reflection components, allowing for more faithful polarization information identification of the isotropy plane and the symmetry axis. The polarization correction also localizes diagonal component energy maxima and off-diagonal component energy minima closer to the true orientation of the principal axes when a range of incidence angles up to 20° is used. / text

This dissertation, a collection of independent papers, explores the polarization of the United States Congress through the lens of primary elections, campaign finance, and party structures during a pivotal moment in American political history. Paper 1 focuses on the top two primary format and its potential in producing moderate candidates and legislators, while Paper 2 expounds on the deleterious consequences it poses for the party system as a whole, particularly in this modern era of both high polarization and high fragmentation. Paper 3 examines the Downsian median voter theorem from the perspective of primary election voters, asking if general election wins/losses beget the nomination of more ideological/moderate nominees next cycle. Ultimately, the article illustrates that the parties instead retain consistent records through both election wins and losses, linked to credibility concerns from position changes as well as the inability of members to disentangle from national party identities. Its companion paper, Paper 4, takes that Downsian question to elites in Washington, D.C. Through original interviews with twenty-three individuals including former members of Congress, leadership, congressional staff, and think tank scholars, I describe the electoral and legislative pressures that prevent officeholders from responding to their median voter, especially among those in swing districts most exposed to the risks of partisan behavior. Paper 5, the final paper, brings together the themes of those preceding it by analyzing the ways in which outside interference, specifically political action committees and more inclusive primary elections, propagates legislative caucus fragmentation and weakens official leadership. This work plays one minor role in providing prescriptive steps to improve and empower channels of dialogue in the U.S. legislative brancha - in spite of larger systemic sorting along geographical and partisan lines - and ensure the mediation of ideology between voters and their elected representatives results in policy solutions rather than gridlock.