Master of Science, The Ohio State University, 2021, Mechanical Engineering

The design of a gearbox is subject to multiple performance requirements that must be met. One such requirement is power density, a metric defined as power transmitted per gear volume or per weight. In aerospace applications, one method of reducing gearbox weight to increase power density has been removing material from gear blanks through the use of thin webs. This study adapts a representative spur gear pair design to investigate the effects of using thin-web gears. A deformable-body model of the gear pair is developed to perform quasi-static and dynamic analyses of the gear pair variations with solid and thin webs, subjected to errors causing the load distribution to skew axially. Under quasi-static conditions, the flexible web deflections are shown to ease some of the adverse effects of gear errors. To determine the dynamic conditions where flexible rim modes could be a factor, impact tests are performed along with a modal analysis using the model. The contributions of these rim modes to the overall dynamic behavior are shown to be modest.

Committee: Ahmet Kahraman PhD (Advisor); David Talbot PhD (Committee Member) Subjects: Engineering; Mechanical Engineering

Master of Science in Biomedical Sciences (MSBS), University of Toledo, 2020, Biomedical Sciences (Medical Physics: Radiation Oncology)

Breast cancer patients are often treated in the prone position to improve dose homogeneity and cosmetic outcome. This is especially common when the patient's anatomy is more pendulous. A breast board is used to support the patient on the treatment table. This breast board creates a source of setup error as well as a source of error in the dose calculations of the treatment planning system. This study looks at two different methods for characterizing the board in the treatment planning system, compares the robustness of two different treatment planning methods across seven patients, and investigates the scatter contribution from the breast board. The first characterizing method was the material override method where a bulk density was assigned to the board shell and interior. The second characterizing method was the ROI type external method where the native CT numbers calculated during the simulation were used. A vertical transmission factor profile of the breast board was produced using each method and compared to the profiles obtained from an experimental setup. Seven previously anonymized patients were retrospectively selected, and two plans were made for each patient using the control point method and the augmented wedge method. The control point method is also known as “field-in-field”. This is when hot spots are covered with MLCs and the relative weights of the fields are changed to remove the hot spot. The augmented wedge method was when wedges and control points were used in the same plan. Planning with wedges alone was found to not be feasible. The plans had to have matching prescription coverage of 95%, as well as similar dose statistics. The robustness was compared by calculating the change in dose to a point in the dose shadow of the board when the board was completely removed, as well as the change in hotspot dose when the isocenter was slightly perturbed. The scatter contribution was investigated by measuring the skin dose of a virtual breast pha (open full item for complete abstract)

Committee: David Pearson (Committee Chair); E Parsai (Committee Member); Nicholas Sperling (Committee Member) Subjects: Physics; Radiation

Doctor of Philosophy (PhD), Wright State University, 2015, Engineering PhD

Integrated r-f passive components such as inductors, transmission lines, transformers etc, form the basic building blocks in r-f integrated circuits (RFICs) such as matching networks, low noise amplifiers (LNAs), synthesizers and r-f mixers. One main challenge faced by current technology developers in integrating r-f components on integrated chip (IC) are related to operation and size. Tremendous efforts were made for overcoming challenges of r-f integrated circuits to meet growing technology demands. In general, r-f devices utilize magnetic materials such as ferrites for their operation for improving device performance and scaling. However, due to material properties and size ferrite materials are poor choices when attempting to scale r-f components. The main focus of this work has been to explore new material properties and investigate applications of ferromagnetic (FM) films as potential solution for device scaling. One attractive property of ferromagnetic materials is low processing temperature and high magnetic saturation which eliminates the need for continuous application of magnetic (d-c) field and are compatible with CMOS technology. The disadvantage of ferromagnetic films is high conductivity which induces ohmic losses and affects r-f device performance. In this work a novel concept of low-loss conductor has been introduced whose conductivity can be modeled by utilizing multilayered superlattice structure. The low-loss conductor is made of artificial layered metamaterial (ARLYM) consisting Ni80Fe20/Cu superlattice. By modeling thickness ratio between superlattice layers the skin effect has been suppressed by increasing skin depth at r-f frequencies. The experimental results presented in this work indicates significant improvement in r-f device characteristics such as inductance, quality factor (85%), loss reduction ratio (70%) etc, operating at r-f frequencies. In addition, application of continuous magnetic field was not required in this work due (open full item for complete abstract)

Committee: Yan Zhuang Ph.D. (Advisor); Marian Kazimierczuk Ph.D. (Committee Member); Henry Chen Ph.D. (Committee Member); Robert C. Fitch Ph.D. (Committee Member); Guru Subramanyam Ph.D. (Committee Member); Robert E. W. Fyffe Ph.D. (Other); Ramana V. Grandhi Ph.D. (Other) Subjects: Electrical Engineering; Electromagnetics; Electromagnetism; Engineering; Nanotechnology; Physics; Quantum Physics; Radiation