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Fabrication and Testing of Polymeric Flexible Sheets with Asymmetric Distributed Magnetic Particles for Biomedical Actuated Devices
This thesis explores a method to fabricate magnetic membranes with asymmetric distribution of particles and their testing as actuators. Focus of this research is to fabricate thin polymeric sheets and thickness range of 120-125µm, with asymmetric distribution of magnetic nano particles, employing micromagnets during the fabrication. The micromagnets are used to localize the magnetic particles during the curing process at selected locations. The effect of the asymmetric distribution of magnetic particles in the membrane is used for the first time. Magnetite (Fe3O4) is used as the magnetic particles that is embedded into a polymeric membrane made of polydimethylsiloxane (PDMS); the membrane is then tested in terms of deflection observed by using a high-resolution camera. From the perspective of the biomedical application, PDMS is chosen for its excellent biocompatibility and mechanical properties, and Fe3O4 for its non-toxic nature. Since magnetic actuation does not require onboard batteries or other power systems, it is very convenient to use in embedded devices or where the access is made difficult. A comparative study of membranes with asymmetric and randomly distributed particles is carried out in this thesis. The asymmetric distribution of magnetic particles can benefit applications involving localized and targeted treatments and precision medicine.
Date:
May 2022
Creator:
Bakaraju, Megha Ramya
System:
The UNT Digital Library
Cold-Formed Steel Member Connections Using BAC Screw Fasteners
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Use of this item is restricted to the UNT Community
In this project, the main research objective is intend to seek criteria for evaluating the capacity of BAC screw fasteners with mixed configuration of waterproof seal washer, sealer tape and different pre-drill holes to determine shear and tension strength values for the screws used in cold-formed steel connections. The thesis presents the design methods and test program conducted to investigate the behavior and strength of the screw connections in shear and tension test. Test results were compared with AISI design provisions to determine if new design equations will be developed for those screws used in BAC cooling tower applications. LRFD resistance factors and ASD safety factors were investigated to the proposed design equations.
Date:
May 2019
Creator:
Li, Xun
System:
The UNT Digital Library
CFD Study of Ship Hydrodynamics in Calm Water with Shear Current and in Designed Wave Trails
Although the capability of computational fluid dynamics (CFD) in modeling ship hydrodynamics is well explored in many studies, they still have two main limitations. First, those studies ignore the effect of non-uniform shear current which exists in realistic situation. Second, the focus of most studies was laid more on the seakeeping/maneuvering performance and less attention was paid to survivability of ships due to extreme ship response events in waves, which are considered rare events but influential. In this thesis, we explore the capability of CFD in those two areas. In the first part of the thesis, the hydrodynamic performance of KCS in the presence of a non-uniform shear current is investigated for the first time using high-fidelity CFD simulations. Various shear current conditions with different directions were considered and results were compared with the ones with no shear current. The second part of the thesis focuses on study of rare events of ship responses by development of extreme response conditioning techniques to design the wave trail. Two conditioned techniques based on Gaussian and non-Gaussian processes are considered.
Date:
May 2022
Creator:
Phan, Khang Minh
System:
The UNT Digital Library
Impact of Processing Parameters and Forces on Channels Created by Friction Stir Bobbin Tools
In this thesis, friction stir channeling (FSC) and its process parameters influence on geometry, surface quality and productivity are explored. The probe of the friction stir processing (FSP) tool used to perform these tests was a modified submerged bobbin tool made of MP 159 Co-Ni alloy. The body was made from H13 tool steel. To find the optimal channel conditions for a targeted range of process parameters, multiple 6061 aluminum samples were prepared with a U shape guide to test the effects of different spindle speeds and feed rates. Using a gantry-type computer numerical control (CNC) friction stir welding (FSW) machine, the aluminum coupons were subjected to calibration experiments, force control tests, and an increased production rate to test these effects. It was found through experimentation that the programmed feed rates, spindle speeds and forces produced by the machine had an impact on the channel geometry. It was determined from the force-controlled setup that 8.46 mm/s at 750 RPM was the best combination of results for the four conditions tested on a CNC friction stir processing-machine. It was then tested at 10.58 mm/s at 800 RPM, which had comparable results with the best combination of input parameters from the force-controlled …
Date:
May 2022
Creator:
Koonce, James G
System:
The UNT Digital Library
Topology and Lattice-Based Structural Design Optimization for Additively Manufactured Medical Implants
Topology-based optimization techniques and lattice structures are powerful ways to accomplish lightweight components with enhanced mechanical performance. Recent developments in additive manufacturing (AM) have led the way to extraordinary opportunities in realizing complex designs that are derived from topology and lattice-based structural optimization. The main aim of this work is to give a contribution, in the integration between structural optimization techniques and AM, by proposing a setup of a proper methodology for rapid development of optimized medical implants addressing oseeointegration and minimization of stress shielding related problems. The validity of the proposed methodology for a proof of concept was demonstrated in two real-world case studies: a tibia intramedullary implant and a shoulder hemi prosthetics for two bone cancer patients. The optimization was achieved using topology optimization and replacement of solid volumes by lattice structures. Samples of three lattice unit cell configurations were designed, fabricated, mechanically tested, and compared to select the most proper configuration for the shoulder hemi prosthesis. Weight reductions of 30% and 15% were achieved from the optimization of the initial design of the tibia intramedullary implant and the shoulder hemiprosthesis respectively compared to initial designs. Prototypes were fabricated using selective laser melting (SLM) and direct light processing …
Date:
May 2019
Creator:
Peto, Marinela
System:
The UNT Digital Library
The Product is People: An Investigation of Missile Combat Crew Perceptions Surrounding Standardized Training Curriculum
Missile Combat Crew members are officers in the United States Air Force responsible for operating nuclear-tipped intercontinental ballistic missiles. They undergo on-the-job training as part of the curriculum necessary to progress in their careers and achieve higher levels of job responsibility. The curriculum they use is created and maintained by 20th Air Force Test and Training Section. This product is known as the Missile Combat Crew Commander Upgrade program, and it has received criticisms from stakeholders who use it for being out of date and failing to capture the necessary topics for ensuring adequate on the job training is being conducted. This project seeks to examine these critiques, break down the curriculum produced by 20th AF into stages (creation, implementation, and feedback) for evaluation, uses principles of user-oriented design drawing on design anthropology to suggest alternative methods for curriculum creation, and utilizes the results of a diagnostic survey to provide data-driven recommendations to 20th AF for future rewrites of their product based on feedback from the crew members who use their product in the field.
Date:
May 2023
Creator:
Hanel, Daniel James
System:
The UNT Digital Library
Nothing Short of Really Healthy Children: Mothers, the Children's Bureau, and Disability, 1914 - 1933
In 1931 the United States Children's Bureau asserted that "nothing short of really healthy children should satisfy parents." This thesis examines how literature published by the Children's Bureau from 1913 to 1933 shaped perceptions of motherhood and of maternal control over the body. As the bureau taught mothers how to care for their children, it also taught them that by following bureau advice, mothers could shape the bodies of their children to adhere to normative body standards. The research considers the relationship between mothers, the state, and the physical body. This thesis is divided into chapters about prenatal care and maternal marking; infant care and maternal policing; and child care and maternal control.
Date:
May 2023
Creator:
Edsall, Brooke C.
System:
The UNT Digital Library
Discriminative Control of Behavioral Variability in Video Game Play
Creativity can be a useful skill in today's classrooms and workplaces. When individuals talk about creativity, it's unclear what the controlling variables are when we tact behavior as "creative." Research in understanding the processes behind behaviors that are considered "creative" would assist in identifying functional relations and provide insight on how to teach creativity. Since creativity is often described as doing something different from the norm, behavioral variability may be a potential aspect of creativity. This study aimed to replicate previous findings by investigating the effects of discrimination training in a multiple schedule of varied and repetitive responding in the context of a video game. Participants played through a 2D online video game made in Bloxels. Different alternating-colored platforms served as the discriminative stimuli for the vary and repeat components. Three parameters of variability were measured (e.g., left jumps, right jumps, and double jumps). The results of the study indicate that participants were able to learn the discrimination of when to repeat and vary their responses depending on which colored platform they encountered.
Date:
May 2023
Creator:
Arias, Gabriela Isabel
System:
The UNT Digital Library
Grand Canyons: Authoritative Knowledge and Patient-Provider Connection
In 2011, African Americans in Tarrant County, Texas experienced an infant mortality rate of 14.3 per 1,000 live births. The leading cause of infant mortality in Tarrant County is prematurity and maternal nutritional status. Both maternal under-nutrition and over-nutrition are known risk factors for premature birth. Improving maternal nutrition, by reducing rates of gestational diabetes and preeclampsia, and by increasing consumption of essential prenatal vitamins and nutrients, is a road to decreasing preterm birth in African Americans. This qualitative study, based on both anthropology and public health theory, of the nutrition behavior of a group of African American expectant mothers and the experience of their health care providers and co-facilitators had a goal to provide a foundation for future development of nutrition behavior research and education for this specific population. The main finding of this study was the substantial gap of lived experience and education between the patients and their providers and co-facilitators, which hinders delivery of care and the patients’ acquiescence to nutrition recommendations. The discrepancies between the authoritative knowledge of the providers and the bodily knowledge of expectant mothers were responsible for the ineffectiveness of nutrition recommendations.
Date:
May 2015
Creator:
Fowler, Rebecca (Public health researcher)
System:
The UNT Digital Library
Multicultural Training and Program Climate in Masters Sport Psychology Programs
Little is known about the current state of multicultural training within sport psychology master's programs. The study explored students' perceptions of their multicultural training and program climate. Importantly, differences in perceptions were investigated based on students' demographic factors, given that students with marginalized identities tend to report less favorable perceptions of and experiences in graduate training. Participants (N = 107) consisted of students and recent graduates of master's level sport psychology programs. Participants reported moderate levels of feeling safe, valued, and comfortable within their master's program, low to moderate levels of multicultural training integration within their curriculum and supervision, and low to moderate satisfaction with their multicultural training. Asian, Asian American, bi/multiracial, Black, African American, Hispanic, and Latino/a/e students, compared to their White peers, reported less satisfaction with their multicultural training, felt less safe, comfortable, and valued within their programs, and perceived less integration of multiculturalism into curriculum and supervision. A multiple regression analysis revealed that, for all students, perceptions of multicultural training integration and reports of feeling safe, comfortable, and valued was significantly related to students' satisfaction with their multicultural training. Discussion focuses on possible explanations for these findings, training implications, and future research directions.
Date:
May 2023
Creator:
Arnold, Macey L.
System:
The UNT Digital Library