The Chesapeake Bay impact structure is one of the largest and most well preserved impact structures on Earth. It has a unique morphology composed of an inner crater penetrating crystalline basement surrounded by a wider crater in the overlying sediments. In 2004, the U.S. Geological Survey conducted a seismic survey with the goals of constraining crater structure and in support of the drilling of a borehole into the deepest part of the crater. Travel-time and waveform inversion were applied to the data to produce a high-resolution velocity model of the crater. Low-fold reflection processing was also applied. Northeast of the crystalline crater, undeformed, eastward-sloping crystalline basement is ~1.5 km deep. The edge of the inner crater is at ~ 15 km radius and slopes gradually down to a depth of 1.5 - 1.8 km. A central peak of 4-5 km radius rises to a depth of ~0.8 km. Basement velocity in the crystalline crater is much lower than undeformed basement, which suggests ~10% fracturing of the crater floor, and up to 20% fracturing of the central uplift. A basement uplift and lateral change of velocity, interpreted as the edge of the transient crater, occurs at a radius of ~ 11 km. Assuming a 22 km diameter transient crater, scaling laws predict a ~30 km diameter crater and central peak diameter of 8-10 km. This indicates that post-impact collapse processes that created the ~ 30 km diameter crystalline crater were unaffected by the much weaker rheology of the overlying sediments. / Master of Science

The Pen Branch Fault is a reactivated, high angle, reverse basin border fault that dips to southeast from the basement (Triassic-Paleozoic-Precambrian in age) to near vertical through the Atlantic Coastal Plain sediments (Late Cretaceous to Recent in age) of the Savannah River site in South Carolina. The fault movement has occurred through Late Cretaceous to Tertiary. Faulting might penetrate as shallow as the Dry Branch and the Tobacco Road Sand Formations (Late Eocene). An investigation with high resolution reflection seismic data is undertaken along the Pen Branch Fault. Five of the seismic lines are reprocessed to help in determining the upward depth of penetration of this fault. This is done by utilizing refracted arrivals from the multifold reflection data. The shallowest refractors (4 - 18 m) imaged have an average velocity of 1700 m/s. All of the lines exhibit events that are not flat lying across the data where the fault is believed to be. The lines possess deformation such as offsets, upwarping and channels. Deformation can be related to the Pen Branch Fault as shallow as 4 m from the surface. Displacements along the lines vary from 1 m up to 5 m. Reverse sense of motion is mainly exhibited along the fault zone that is covered by this study. The events resolved portray the Pen Branch Fault in a fault zone of subparallel faults and splays. / Master of Science

Single-mode optical fiber has been widely used not only in long-haul, high speed digital communication systems but also in sensing applications because of its inherent immunity to electromagnetic interference, low transmission loss, wide bandwidth, small size, and light weight. Birefringence is an important parameter of the optical fiber, determining bandwidth in fiber optic telecommunications, and resolution in fiber optic sensors. This thesis describes and demonstrates permanent photo-induced rotation of the principal axes of birefringence in Ge-doped circular-core low-birefringence single-mode optical fiber. Light from a linearly polarized Ar⁺ laser at a wavelength of 488 nm was launched into the fiber along one of the principal axes of the initial birefringence in the fiber. Rotation of the principal axes was observed after several hours of exposure. This observation helps one to understand the mechanism of the photo-induced effects in Ge-doped optical fiber, and to discover possible ways to control the birefringence in the fiber by means of photo exposure. / Master of Science

On August 31, 1886 a large scale earthquake occurred in Summerville, S.C. causing severe damage in the coastal city of Charleston. Although intensive geological and geophysical studies have been conducted in the area, uncertainty remains about the details of the event. Recently evidence from seismic reflection profiles have shed light on the tectonic environment of the area. The epicentral area of the 1886 event lies within the South Georgia Rift, a Mesozoic rift terrane. Previous studies have revealed clues to the geologic structure and evolution of this feature. SEISDATA4 is the largest seismic reflection profile recorded in the area. By re-processing the line, information about the tectonic structure of the area was revealed. The early Mesozoic extensional basin that hosted the 1886 earthquake and is host to the modern seismicity recorded in the area, extends several kilometers to the south and west of Charleston, along SEISDATA4. Cenozoic and Mesozoic faults were resolved within the basin and along its northwestern boundary that is distinguished by a strong gradient in the magnetic field. However, the question as to which fault was responsible for the rupture of 1886 still remains. The refraction analysis provides better resolution of the lithology in Lower Mesozoic section. The termination of the strong reflection at the base of the Atlantic Coastal Plain occurs in a section of the profile that shows major disruption of the underlying reflections, and suggests that the termination of a lower Mesozoic basalt flow responsible for the reflection may be related to tectonic deformation. / Master of Science

This research was inspired by a need to discover more refined technologies for imaging growing joints to facilitate research in childhood arthritis, which is among the most common chronic conditions of childhood. The objective of this project was to develop and test a new technology for imaging growing joints using diffraction enhanced imaging (DEI) combined with computed tomography (CT) using a synchrotron radiation source. DEI is a modality that derives contrast from x-ray refraction, extinction (an extreme form of scatter rejection), and absorption (as in conventional radiography). The ability to add to an image’s contrast from the refraction of x-rays, rather than that solely from absorption, generates more detailed visualization of soft tissue and of interfaces between tissues. Additionally, refraction-based imaging allows reduction of absorbed radiation dose by the sample tissue. For this research, stifle joints from four-week piglet joints were imaged by DEI-CT using the BioMedical Imaging and Therapy (BMIT) beamline at the Canadian Light Source (CLS) synchrotron facility. This new modality for imaging growing joints incorporated a novel feedback control to maintain precise alignment of the analyzer crystal, which is used to re- diffract the beam that passes through the object, throughout the scanning procedure. Results showed that high-resolution DEI-CT provided three-dimensional images of the bone and soft tissue of growing joints at a resolution on the order of microns. Fine detail within and between all joint structures and tissues, including striking detail of cartilage vasculature, a iii characteristic of growing but not mature joints, was demonstrated. This report documents for the first time that DEI combined with CT and using a synchrotron radiation source can generate more detailed images of intact, growing joints than is currently available from conventional imaging modalities. The development of this high resolution imaging system, which provides excellent contrast for both hard and soft tissues, fills an important gap in the suite of imaging modalities available for joint research, particularly during growth.

Prevailing propagation phenomena in certain areas play a vital role in deciding terrestrial wireless systems performance. Vertical refractivity profile below 1 km is a critical parameter for designing reliable systems; noting that there is a shortage of upper-air data worldwide. Anomalous phenomena may cause severe signal fading and interference beyond the horizon. The objectives of this thesis are to investigate dominant refractive conditions in the subtropical Arabian Gulf region, develop new approaches and empirical models for evaluating vertical refractivity profiles and relevant propagation parameters in the low troposphere, and to examine the impact of frequently experienced anomalous phenomena on terrestrial microwave links. Twenty-three years of meteorological measurements, from 1990 to 2013, are utilized using spatially separated surface stations and a single radiosonde in the United Arab Emirates (UAE). Profiles of sea level, surface and upper refractivity components are statistically analysed. Three major atmospheric layers; namely 65 m, 100 m and 1 km above the ground are studied to analyse relevant propagation parameters such as sub-refraction, super-refraction, anomalous propagation probability parameter β0 and point refractivity gradient not exceeded for 1% of time. The effective earth radius factor k is investigated using a new weighted averaged approach. In addition, the seasonal structure of atmospheric ducting is dimensioned within 350 m layer above ground. Finally, microwave measurement campaign is conducted using multiple radio links operating in UAE using various frequency bands. The link budget simulations are compared with the signal strength measurements. Fading scenarios are studied against the observed anomalous conditions and several recommendations are concluded.

Prevailing propagation phenomena in certain areas play a vital role in deciding terrestrial wireless systems performance. Vertical refractivity profile below 1 km is a critical parameter for designing reliable systems; noting that there is a shortage of upper-air data worldwide. Anomalous phenomena may cause severe signal fading and interference beyond the horizon. The objectives of this thesis are to investigate dominant refractive conditions in the subtropical Arabian Gulf region, develop new approaches and empirical models for evaluating vertical refractivity profiles and relevant propagation parameters in the low troposphere, and to examine the impact of frequently experienced anomalous phenomena on terrestrial microwave links. Twenty-three years of meteorological measurements, from 1990 to 2013, are utilized using spatially separated surface stations and a single radiosonde in the United Arab Emirates (UAE). Profiles of sea level, surface and upper refractivity components are statistically analysed. Three major atmospheric layers; namely 65 m, 100 m and 1 km above the ground are studied to analyse relevant propagation parameters such as sub-refraction, super-refraction, anomalous propagation probability parameter β0 and point refractivity gradient not exceeded for 1% of time. The effective earth radius factor k is investigated using a new weighted averaged approach. In addition, the seasonal structure of atmospheric ducting is dimensioned within 350 m layer above ground. Finally, microwave measurement campaign is conducted using multiple radio links operating in UAE using various frequency bands. The link budget simulations are compared with the signal strength measurements. Fading scenarios are studied against the observed anomalous conditions and several recommendations are concluded.

published_or_final_version / Earth Sciences / Master / Master of Science

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Baigiamajame magistro darbe analizuojami Lietuvos geodezinio vertikaliojo pirmosios klasės tinklo linijos Jonava – Zarasai niveliavimo rezultatai. Darbe apžvelgtos vertikaliojo tinklo sudarymo nuostatos, šalies dalyvavimas tarptautiniuose projektuose, sudarytas vertikalusis pirmosios klasės tinklas, vertikaliojo tinklo sudarymo metodika bei prietaisai ir priemonės, naudojami šio tinklo matavimuose. Darbe pateikti eksperimentiniai nivelyrų sistemos kalibravimo rezultatai ir pavienių matuoklių kalibravimo rezultatai. Pateikiama niveliavimo duomenų apdorojimo metodika. Baigiamajame darbe pagal nivelyrų sistemos bei pavienių matuoklių kalibravimo rezultatus nagrinėjamos kalibravimo, refrakcijos ir temperatūros pataisos, analizuojamas nesąryšių ir temperatūros kitimas vertikaliojo tinklo linijoje Jonava – Zarasai, skaičiuojamas niveliavimo rezultatų tikslumas. Darbo pabaigoje pateikiamos išvados. Darbą sudaro: įvadas, 4 skyriai , išvados, literatūros ir kitų šaltinių sąrašas. Darbo apimtis – 70 p. teksto be priedų, 44 iliustr., 11 lent., 34 bibliografiniai šaltiniai. Atskirai pridedami darbo priedai. / Master's thesis aim - analysis of the levelling results of the vertical network line Jonava – Zarasai. At work is described technical regulations of the vertical network, first order vertical network and also used measurement technique. At work is presented experimental results of digital levels system calibration and results of levelling stuffs calibration. By these results in this work is performed analysis of refraction, calibration and temperature corrections, and also analysis of the air temperature and heights differences mismatching. At work also was calculated leveling accuracy. In the end of the work is presented conclusions. Structure: introduction, 4 chapters, conclusions and suggestions, references. Thesis consist of: 70p. text without appendixes, 44 pictures, 11tables, 34 bibliographical entries. Appendixes included.