Doctor of Philosophy, The Ohio State University, 2024, Biomedical Engineering

The lens is the pivotal tissue of the eye allowing accommodation, the process by which the eye adjusts focal distance. Presbyopia and cataract, age-associated lens dysfunctions, prevent proper accommodative function and focusing of light as it passes through the lens. As the eye ages, lenses continue to grow in size and stiffen. As these properties change with age, lenticular dysfunctions arise. Presbyopia is incredibly common, impairing near vision in nearly all people by 40 to 50 years of age. A significant portion of the population lives with imperfect near vision due to presbyopia. The exact causes of presbyopia are yet to be explained, and additionally, there remain no effective therapies capable of restoring, or preventing the loss of, full accommodative function in aged lenses. It is now understood that both lens stiffening and lens geometric change due to continual lens growth, lead to presbyopia. Recent studies have demonstrated that mechanical force transduction, through the zonular fibers to the lens capsule, increases lens epithelial cell proliferation. These findings offer an avenue of study that could reveal mechanisms governing lens growth and guide future lens treatment options. Some clinical practitioners consider presbyopia and cataract to be entirely treated through the use of spectacles and implanted artificial intraocular lenses; however, no preventative therapy exists and no current treatment is capable of restoring accommodation. Advancement in the understanding of lens cell biology, mechanics, and the lens epithelial cell (LEC) mechanobiological response is necessary for the improvement of clinical treatment for age-associated lens dysfunction. This dissertation seeks to describe a new branch in the field of lens study with hopes of expanding fundamental knowledge focusing on LEC growth and mechanobiology. First, a novel method of simulating accommodation-like forces in a murine eye model is detailed. The methods described here demo (open full item for complete abstract)

Committee: Katelyn Swindle-Reilly (Committee Member); Cynthia Roberts (Committee Member); Heather Chandler (Committee Member); Matthew Reilly (Advisor) Subjects: Biology; Biomechanics; Biomedical Engineering; Biomedical Research; Ophthalmology; Optics

Master of Science in Engineering (MSEgr), Wright State University, 2007, Electrical Engineering

Digital wideband receivers are essential elements used in electronic warfare (EW) applications. Instantaneous Frequency Measurement (IFM) receivers are suitable for use in EW systems due to the ultrawide instantaneous radio-frequency (RF) bandwidth, fine-frequency resolution, and moderately high sensitivity and dynamic range. Conventional IFM receivers use analog components such as power dividers, crystal video detectors, and hybrids. This research presents the architecture and design implementation of a purely digital IFM receiver based on a patented algorithm courtesy of the United States Air Force. The invention is capable of detecting a short wave pulse with 1 MHz error for every 100 nsec. The benefits include a compact, lightweight, cost-effective alternative to its analog counterpart. The design was implemented and tested on Delphi's ADC3255 (a PMC digitizer with Xilinx Virtex 4 FPGA). The outputs were verified using Xilinx's ChipScope Pro.

Committee: Henry Chen PhD (Advisor); John Emmert PhD (Other); Raymond Siferd PhD (Other); Joseph Thomas Jr., PhD (Other) Subjects:

Master of Science, University of Akron, 2009, Electrical Engineering

The main purpose of this research study was to explore the potential application of polarimetric principles in characterization and monitoring of space materials. Space monitoring and collision avoidance between space vehicles and inter-space debris has become a major concern for space agencies and authorities maintaining satellites, space shuttles and stations. Inter-space debris can be man-made or natural. As the quantity of space debris increases, tracking and collision avoidance becomes a critical issue. The novelty of this study consists in the single pixel analysis of back scattered optical polarimetric signatures from various space materials. Surface characterization of different materials was performed by analysis of their polarization response. The study employed single-pixel detection of back scattered laser beam polarimetric signatures obtained from different materials. The back scattered optical polarimetric signatures contained major information related to geometry, texture and composition of the material. The DOLP (Degree of Linear Polarization) algorithm was applied to analyze polarization response from the different materials used in this study. Different materials used in space vehicle design were examined and the DOLP ratio was calculated at different material and detector orientations. On examining Teflon, which is a soft polymer material used in space vehicle design, we observed high depolarization of light. This was due to the “Diffuse reflectance” nature of Teflon at different object orientations. Hence, Teflon can be identified as a “Lambertian surface” exhibiting high depolarization of light. The polarization response exhibited by materials such as windowless polysilicon solar panel and a wooden stick painted in white color mixed with titanium dioxide was found to be similar to the response exhibited by Teflon. It was observed that the extent of depolarization exhibited by different materials was found to be distinct and depended on materia (open full item for complete abstract)

Committee: George Giakos Dr. (Advisor) Subjects: Electrical Engineering

Master of Science, University of Akron, 2005, Civil Engineering

Polymer Matrix Composites (PMC) are increasingly favored in structural applications for their light weight and durability. However, the numerical modeling of these materials poses several challenges. This is primarily due to the highly anisotropic nature of the creep exhibited by these materials above the glass transition temperature. Also, the damage and failure of the material is of particular interest to designers using the PMCs. Recently, a sustained effort has been to provide the designer with large computer codes containing comprehensive constitutive equations, often equipped with large number of internal variables and with the most general mathematical forms, for use in structural design analysis. Although elegant and useful, such constitutive laws are often expensive in implementation. Specially for early stages of the design, a quicker way of estimating complicated PMC behavior is needed. In this work, the constitutive material law by Robinson and Binienda (2001) [1,2] is utilized for such an approach. The model is successful in describing polymer matrix composite (PMC) materials having long or continuous reinforcement fibers embedded in a polymer matrix. Although the material law includes a single scalar parameter to describe the damage, it retains the essential material behavior. The material law is implemented computationally as a user defined subroutine (UMAT) in a commercially available FEA code (ABAQUS). The material parameters are obtained from experiments of thin-walled tubular specimens reinforced with unidirectional, helical fibers at an angle , and under tensile and shear loading . The model correctly predicts the relation between logarithmic creep rate and logarithmic stress. The user subroutine has robust convergence properties. The creep strain rate and the effect of damage on the creep strain rate are presented for the benchmark problem of a square plate with a circular hole at the center and pressure vessel. The effect of fiber orientation o (open full item for complete abstract)

Committee: Wieslaw Binienda (Advisor) Subjects: Engineering, Civil