Sensing in scattering environments, such as fog and dust, poses a serious challenge for all optical systems and is important for many critical surveillance applications. The use of polarized light, specifically circularly polarized light, has shown great promise for improving detection range and sensing in highly scattering, real-world environments. While the potential impact to application is significant, the optical science and sensing community lacks data on broad wavelength and environmental parameters where circularly polarized light outperforms linearly polarized light, increasing detection range and signal persistence. In this dissertation I quantify, through simulation and experimental results, the advantage of circularly polarized light in laboratory and real-world scattering environments - focusing on circularly polarized light's superior persistence in these environments. I present new and unique contributions to the study of polarized light in both isotropic (Rayleigh regime) and forward-scattering environments, showing circular polarization's superior persistence increases detection range for real-world environments over broad wavelength and particle size regimes. Utilizing polarization-tracking Monte Carlo simulations for varying particle size, wavelength, and refractive index, I quantify when circular polarization outperforms linear polarization in maintaining the illuminating polarization state for large optical thicknesses, persisting to longer ranges. I identify many real-world environments with particle sizes of radiation fog, advection fog, and Sahara dust where circular polarization outperforms linear polarization over broad wavelength ranges in the infrared spectrum. This enhancement with circular polarization can be exploited to improve sensing range and target detection in obscurant environments that are important in many critical surveillance applications. Conversely, I also identify a few environmental configurations where linear polarization outperforms circular polarization. However, circular polarization's response is generally larger and over broader wavelength ranges in the infrared regime for real-world scattering environments. Experiments were conducted for both 1) isotopically-scattering (Rayleigh regime) environments and 2) forward-scattering environments using polystyrene microspheres with well-defined diameters. These measurements demonstrated that in the forward-scattering environments, circular polarization persists through increasing optical thickness better than linear polarization. Variations in persistence were investigated as a function of collection geometry, angular field of view, and collection area. Persistence for both linear and circular polarization was found to be more susceptible to collection geometry, specifically increased collection area, in the isotropically-scattering (Rayleigh regime) environment. Similarly, linear polarization in the forward-scattering environments is dependent upon changes in collection geometry. Significantly, circular polarization's response is nearly unaffected by variations of both field of view and collection area for the forward-scattering environments. Circular polarization proves to be not only generally better in persistence but also more tolerant of variations in angular collection and collection area compared to linear polarization, making it ideal and flexible for use in optical sensing systems in scattering environments. Finally, I present simulation results that show the evolution of linear and circularly polarized light as it scatters throughout both isotropic (Rayleigh regime) and forward-scattering environments as a function of scattering event. Circularly polarized light persists through a larger number of scattering events longer than linearly polarized light for all forward-scattering environments; but not for scattering in the Rayleigh regime. Circular polarization's increased persistence occurs for both forward and backscattered light. The evolution of the polarization states as they propagate through the various environments are illustrated on the Poincaré sphere after successive scattering events. This work displays individual scattering events as well as a cumulative, measureable result, in an intuitive manner. Throughout this dissertation I quantify the polarization persistence and memory of circularly polarized light in real-world scattering environments over broad wavelength, particle size, and collection-geometry parameter spaces; and for the first time, detail the evolution and modification of both circularly and linearly polarized states through isotropic and forward-scattering environments. These results show how circular polarization can extend range and sensing capability in surveillance sensing applications in real-world scattering environments.

Philosophiae Doctor - PhD / Low- and medium-spin bands of 187Os have been studied using the AFRODITE array, following the 186W(4He,3n)187Os reaction at a beam energy of 37 MeV. The measurements of 􀀀 coincidences, angular distribution ratios (RAD), polarization and -intensities were performed using eleven High Purity Germanium (HPGe) clover detectors. In the current work, all the previously known bands have been signi cantly extended and ve new bands have been added to the level scheme. The observed bands are interpreted within the cranked shell model (CSM), cranked Nilsson-Strutinsky- Bogoliubov (CNSB) formalism and Quasiparticle-plus-Triaxial-Rotor (QTR) model. Systematic comparison of bands with the neighbouring isotopes has also been made. Comparison of the models with experimental data shows good agreement.

<p> The properties of the levels of 21Ne and 29Si have been studied via γ-ray angular distribution and linear polarization measurements and γ-γ coincidence studies yielding a number of new spin-parity assignments to the states of both nuclei. Comparison of the results with the Nilsson model for odd nuclei indicate that for 21Ne, good agreement is in general obtained. Nevertheless, a number of interesting discrepancies exist with regard to the negative parity states of 21Ne and explanations have been proposed for some of these. The agreement is also quite good for 29Si with a calculation using a minimum of free parameters, confirming the oblate shape for this nucleus.</p> / Thesis / Doctor of Philosophy (PhD)

Severe corrosion damage and even complete failure was recently discovered in external post-tensioned (PT) tendons of three Florida's pre-cast, segmental bridges over seawater. A key deterioration factor was the formation of large bleed water grout voids at or near the anchorages. Steel corrosion may occur at the grout-void interface or in the air space of the void itself. Since the tendons are critical to the structural integrity of the bridges, reliable and non-intrusive damage detection methods are desirable to manage or prevent future occurrences. In recent years several indirect non-destructive methods have been developed or improved to evaluate the conditions of the tendons. One of those methods is vibration-based tension measurements, consisting of detecting tendon tension loss by analyzing the tendon's natural frequencies. Until recently, vibration-based tension measurements were costly and laborious since they required several operators to conduct the tests and complicated analysis through different programs. The first objective of this research is to provide a practical, simplified, user-friendly testing and analysis method for screening tendons by vibration measurements. Electrochemical Impedance Spectroscopy, Linear Polarization, and Electrical Resistance are alternative methods that could nondestructively detect or monitor corrosion before strand failures occur. The reliability and sensitivity of these conventional monitoring methods in solid or liquid media are well proven. However, few investigations exist on applying these methods to air-space corrosion as it may occur in tendon anchors. The second objective of this research is to establish the feasibility of using the above conventional monitoring methods for detecting air-space corrosion. In this investigation, two different types of Electrical Resistance probes were designed and evaluated. Also, electrochemical probes were constructed simulating strands conditions in the grout-void interface. Electrochemical Impedance Spectroscopy and Linear Polarization measurements were conducted in the electrochemical probes to calculate their instantaneous corrosion rates. Electrical Resistance and Electrochemical probes results indicate that both methods provide sufficient sensibility to determine the ongoing damage.

Philosophiae Doctor - PhD / Lying in a rapidly-changing transitional region between nuclei that may behave as spherical vibrators (N ≤ 88) or good rotors (N ≥ 92), the N = 90 isotones present a unique testing ground where new nuclear collective phenomena may be uncovered. As part of a general investigation of collective structures and the coupling of single-particle states to these structures, the 150Sm(12C,4nγγ) and 150Sm(13C,4nγγ) reactions at a beam energy of Elab = 65 MeV were used to study the low and medium spin structure of 158,159Er nuclei below spin 20~. The γ-γ coincidence events were detected in the nine escape-suppressed HPGe Clover detectors using the AFRODITE γ-ray spectrometer at the iThemba Laboratory for Accelerator Based Sciences. DCO ratios and γ-ray polarization measurements were used to establish the spins and parities of newly observed and confirm previously established rotational bands. The observed bands will be discussed in terms of both traditional quadrupole rotational-vibration models and recent predictions of octupole correlations in the N = 90 isotones and neighbouring nuclei. The data obtained will be compared with the spectroscopic systematics of neighbouring nuclei.

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The quality and quantity of polarimetric data being collected for stellar sources creates new opportunities for studying stellar properties and evolution, and also leads to new challenges for modeling and interpreting such data. Inspired by fresh prospects for detecting the Hanle effect to study photospheric magnetic fields, we have focused attention on purely geometrical aspects for polarimetric variability in the example of oblique magnetic rotators. In the case of axisymmetric fields, we highlight two key facts: (a) polarimetric lightcurves necessarily exhibit a certain time symmetry with rotation phase, and (b) variations in the polarization position angle can be modeled based on geometrical projection effects, independent of the photospheric magnetic field. These conclusions also have general applicability, such as to Thomson scattering and the transverse Zeeman effect. The authors gratefully acknowledge that funding for this work was provided by the National Science Foundation, grant AST-0807664.

Philosophiae Doctor - PhD / Low- and medium-spin bands of 187Os have been studied using the AFRODITE array, following the 186W(4He,3n)187Os reaction at a beam energy of 37 MeV. The measurements of γ − γ coincidences, angular distribution ratios (RAD), polarization and γ-intensities were performed using eleven High Purity Germanium (HPGe) clover detectors. In the current work, all the previously known bands have been significantly extended and five new bands have been added to the level scheme. The observed bands are interpreted within the cranked shell model (CSM), cranked Nilsson-StrutinskyBogoliubov (CNSB) formalism and Quasiparticle-plus-Triaxial-Rotor (QTR) model. Systematic comparison of bands with the neighbouring isotopes has also been made. Comparison of the models with experimental data shows good agreement. The configurations of some of the previously observed bands have been modified. Most importantly, the coupling of 2+ γ band to the 11/2+[615] neutron configuration is observed for the first time.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18284号 / 工博第3876号 / 新制||工||1595(附属図書館) / 31142 / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 野田 進, 教授 川上 養一, 教授 藤田 静雄 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

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