Ph.D. - Mechanical Engineering
Permanent URI for this collection
Browse
Recent Submissions
Item Dynamic compressed sensing and coverage optimization for multi-agent systems(2025) Shriwastav, Sachin; Zhu, Frances; Mechanical EngineeringItem Tendon-driven notched needle manipulation, guidance, and modeling in soft tissue under real-time ultrasound tracking(2025) Padasdao, Blayton Kenji; Konh, Bardia; Mechanical EngineeringItem Chemotactic behavior for a self-phoretic janus particle near a patch source of fuel(2025) Mancuso, Viviana; Uspal, William E.; Mechanical EngineeringItem THIN FILM GAS ADSORPTION MEASUREMENT AND CONTROL(2024) Pham, Thi Kieu Ngan; Brown, Joseph; Mechanical EngineeringItem Using Battery Energy Storage Systems to Address the Needs of Different Types of Grid Participants(2024) Angelo, Michael S.; Ghorbani, Reza; Mechanical EngineeringItem THERMAL TRANSPORT IN POLYMER NANOFIBER AND POLYMER NANOCOMPOSITES(2025) Nguyen, Anh Tuan; Lee, Woochul; Mechanical EngineeringItem SYNTHETIC VOLTAGE DATASETS FOR ARTIFICIAL INTELLIGENCE-BASED LI-ION DIAGNOSIS AND PROGNOSIS: INVESTIGATION OF THREE DIFFERENT BLENDING CONDITIONS(2024) Beck, David; Dubarry, Matthieu MD; Mechanical EngineeringItem Biophysical Study Of Tear Film Lipid Layer(University of Hawaii at Manoa, 2023) Xu, Xiaojie; Zuo, Yi; Mechanical EngineeringTear film lipid layer (TFLL) is the outmost layer of the tear film. The current consensus is that the 40-nm thick TFLL consists of two sublayers, i.e., a polar lipid layer covering the air-water surface of the cornea, and a nonpolar lipid layer that resides upon the polar lipids and is directly exposed to air. The polar lipids account for 20 mol% of the TFLL, including ~ 12 mol% phospholipids, and ~ 4 mol% (O-acyl)-ω-hydroxy fatty acids (OAHFAs), which belongs to a newly discovered class of endogenous lipids termed fatty acid esters of hydroxy fatty acids (FAHFAs). The nonpolar lipids account for 80 mol% of the TFLL, with wax esters (WEs, accounting for ~ 43 mol%) and cholesteryl esters (CEs, accounting for ~39 mol%) being the most prevalent nonpolar lipid classes. The major physiological function of the TFLL is to stabilize the tear film by reducing surface tension and retarding evaporation of the aqueous layer. Dysfunction of the TFLL leads to dysfunctional tear syndrome, with the dry eye disease (DED) being the most prevalent eye disease affecting 10-30% of the world population. It is estimated that the DED directly and indirectly causes a $55 billion annual economic burden in the United States alone. To date, except for treatments alleviating the dry eye symptoms, effective therapeutic interventions in treating the DED are still lacking. Therefore, there is an urgent need to better understand the biophysical function of the TFLL and to develop translational solutions in effectively managing the DED. The focus of this dissertation is to study biophysical properties of the TFLL using a newly developed experimental methodology called constrained drop surfactometry (CDS). Main contributions fell into the following four headings: 1. Study of the composition-functional correlations of a model TFLL, under physiologically relevant conditions. For the first time, this study unveiled that the primary biophysical function of FAHFAs is to optimize the interfacial rheological properties of the TFLL. 2. Study of the polymorphism and collapse mechanism of FAHFA monolayers. This study revealed that FAHFA molecules at the air-water surface demonstrate unique polymorphic behaviors, which can be explained by configurational transitions of the molecules under various lateral pressures. 3. Development of a novel ventilated, closed-chamber, droplet evaporimeter with a constant surface area. This droplet-based evaporimeter is capable of a rigorous control of environmental conditions, including the temperature, relative humidity, airflow rate, surface area, and surface pressure, thus allowing for reproducible water evaporation measurements over a time period of only 5 minutes. The volumetric evaporation rate of this droplet evaporimeter is less than 2.7 μL/min, comparable to the basal tear production of healthy adults. This study demonstrated that the TFLL resists water evaporation with a combined mechanism by increasing film compactness of the polar lipid film at the air-water surface, and, to a lesser extent, by increasing film thickness of the nonpolar lipid film. 4. Comparative study of the dynamic surface activity, interfacial rheology, evaporation resistance, and ultrastructure of the meibomian lipid films extracted from wild type (WT) and Soat1 knockout (KO) mice. Inactivation of Soat1 gene led to a complete stoppage of CE production in meibomian glands and a severe change in the eye phenotype in experimental animals. Lipidomic analysis with ultrahigh-pressure liquid chromatography ̶ mass spectrometry showed that the pool of cholesterol rose seven times in the KO mice compared with their WT siblings, and, an almost complete ablation of CEs longer than C18-C20 was observed. This study revealed novel experimental evidence about the composition-structure-functional correlations of the meibomian lipid films. Overall, research in this dissertation advanced the biophysical understanding of the TFLL, and provided novel implications in the pathophysiological and translational understanding of DED.Item Analytical and numerical studies of the effect of shape on microswimmer propulsion(University of Hawaii at Manoa, 2023) Poehnl, Ruben; Uspal, William E.; Mechanical EngineeringThe shape of an active colloid has an enormous effect on the motion of the particle and allows for significantly more variation in its design and application. In this thesis, the dynamics of both convex (spheroidal) and concave (helical and toroidal) particles are investigated with analytical and numerical methods. Starting with an individual particle, it is shown that breaking symmetries of the particle shape can enlarge the possibilities for particle motion, both for self-diffusiophoretic microswimmers and within the more general ``squirmer model''. These results are then extended to include pair interactions. For interacting spheroids, two types of stable pair configurations can exist: co-moving "head-to-tail`` and stationary "head-to-head" pairs. We also consider the interaction of a torus and sphere, with a view towards designing "lock-and-key" interactions.Item Renewable Energy Trading in Real Time Using Simulated Clients and Energy Markets(University of Hawaii at Manoa, 2023) Sariri, Shawyun; Ghorbani, Reza; Mechanical EngineeringRenewable energy has long been seen as a way to alleviate reliance on fossil fuels, this has become even more imperative as the frequency of natural disasters has increased, and the consequences of climate change have become more abundant. However, renewable integration is not a straightforward process as many factors, such as geography, resource availability, cost, legislation, climate, and the stochastic nature of renewables play a factor in what sources can be utilized and in what quantities. Regions cannot go to 100% renewables overnight; a more realistic approach would be to blend already existing grid infrastructure with sustainable energy sources. Because the current grid infrastructure was not initially designed to handle renewable integration, it is important to understand how sustainable sources can work with existing infrastructure. This research proposes a potential testbed to study the effects of how homes can become prosumers to not only lower costs and integrate renewable energy, but to also provide resilience to the power grid. A real-time model is examined to show the potential for a home to produce and sell energy in the current grid as well as how this idea can be integrated into the current grid infrastructure. In addition, a renewable energy marketplace is explored to understand how energy vendors and consumers can interact in real time.