Master of Science in Engineering, University of Akron, 2019, Mechanical Engineering

The proliferation of MEMS devices, especially their use in remote and harsh environments, has prompted the need for novel methods of supplying power. Energy harvesting is one such attractive approach, converting energy from the device's environment into usable power and eliminating the need for external batteries. There are boundless sources of thermal energy (vehicle exhaust, industrial chemical reactions, etc.) from which to harvest. However, energy harvesting systems, especially within thermal applications, exhibit inherent limitations which must be overcome. In this work, a thermally-actuated energy harvester utilizing a combination of shape memory alloys and mechanical frequency up-conversion is designed. The equations of motion for the system are presented, including physically accurate models of a bistable mechanism and shape memory alloy constitutive behavior. Finally, the system is studied in various configurations through exhaustive numerical simulation to characterize system performance and optimize energy harvesting efficiency.

Committee: D. Dane Quinn PhD (Advisor); S. Graham Kelly PhD (Committee Member); Kevin Kreider PhD (Committee Member) Subjects: Applied Mathematics; Design; Energy; Materials Science; Mechanical Engineering; Mechanics; Metallurgy

PhD, University of Cincinnati, 2015, Arts and Sciences: Chemistry

This dissertation is mainly based on the works of synthesis and characterization of self-assembling polymers using hydrogen bonding or hydrophobic interactions. Firstly, N-alkyl urea peptoid oligomer was synthesized as backbone of supramolecular polymers through three step repetition cycles with high yield. One N-alkyl urea peptoid precursor was explored to simplify the synthetic process. 4 different functional groups were converted from one precursor. Then 2-ureido-4[1H]-pyrimidinone (UPy) group which is a quadruple hydrogen bonding system was incorporated to N-alkyl urea peptoid oligomers to generate supramolecules. With the experience of UPy unit, we further explored UPy containing monomer to make organogelators. Three different monomers with different Tg values were copolymerized using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Organogels were afforded in both chloroform and dichlorobenzene. Critical gelation concentration and mechanic properties of organogels were examined. Cooperating another novel monomer containing pyrene unit to the above copolymers, fluorescent organogels were achieved which were suitable for potential up-conversion applications. In addition to pyrene, anthracene is another molecule which shows great up-conversion property. A series of Poly[(9-anthrylmethyl methacrylate)-co-(methyl methacrylate)] (Poly(AnMMA-co-MMA)) with different AnMMA ratios were synthesized via RAFT polymerization, resulting in tunable inter-chromophore distances. These polymers can serve as emitters, with PtOEP as sensitizer, in triplet-triplet annihilation up-conversion (TTA-UC) systems. TTA-UC intensity of the Poly(AnMMA-co-MMA)/PtOEP mixtures displays interesting dependence on the AnMMA ratio in the polymer. Interactions between chromophores on the same polymer chain play the key role in affecting the TTA-UC intensity in these systems. It is critical to minimize intra-chain chromophore quenching in order to achieve high UC intensity. H (open full item for complete abstract)

Committee: Neil Ayres Ph.D. (Committee Chair); David Smithrud Ph.D. (Committee Member); Peng Zhang Ph.D. (Committee Member) Subjects: Chemistry

Master of Science, The Ohio State University, 2011, Chemistry

It is well known that proteins play essential roles in the proper functioning of all biological systems. Protein hydration dynamics are of fundamental importance to a protein's structure and function as well as its recognition and interaction with substrates. It has become a consensus in the field of biochemistry that protein function, structure and dynamics are closely related, among which the dynamics holds the key to understanding how protein structure ultimately determines its biological functions. Here, we will discuss a thorough investigation of protein conformation dynamics and local hydration dynamics at the most fundamental level by integrating state-of-the-art femtosecond laser spectroscopy technology and molecular biology techniques (such as site-directed mutagenesis). Protein conformational fluctuations can occur on many timescales, but it is the ultrafast dynamics that are still not well understood. By using an intrinsic tryptophan as the local optical probe, this group has developed optical techniques that would allow one to see, in real time, ultrafast protein hydration dynamics. The understanding of these dynamics has far-reaching implications relating to protein plasticity and recognition, protein folding and aggregation, and enzyme catalysis. With site-directed mutagenesis, tryptophan was chosen as a local optical probe, and was placed at desired positions on the peptide or protein surfaces to detect environmental response using the femtosecond-resolved fluorescence up-conversion technique. This revealed hydration dynamics with single-residue resolution. Systematic studies were first performed on small model systems, such as α-helix, β-hairpin, and a 20 residue globular protein - termed tryptophan-cage. These systems clearly show that an ordered, rigid water network has been formed even for simple secondary structures. Next, a large and flexible globular protein, calmodulin, was chosen to map the global surface hydration dynamics. For comparison, t (open full item for complete abstract)

Committee: Dongping Zhong PhD (Advisor); Thomas Magliery PhD (Advisor) Subjects: Biochemistry; Biology; Chemistry; Physical Chemistry; Physics