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The research described in this thesis investigates the area of subband coding of high quality digital audio signals. The research into the application of a nonuniform filter bank employing frequency warping to digital audio coding is described. Firstly, some aspects of psychoacoustics, especially masking effects, are studied. Utilising psychoacoustic models, perceptual entropies are calculated for a number of audio excerpts and it is shown that theoretically the bit rate can be reduced to lower than 2 bits per sample. Different types of filter banks are reviewed. To examine the best band splitting scheme, studies are carried out on optimum bit allocations for uniform and nonuniform filter banks, with or without a psychoacoustic model. The concept of perceptual coding gain is proposed and it is shown experimentally that band splitting according to the auditory critical band rate is not recommended for audio compress10n. A new generic nonuniform decomposition algorithm, relying on cascading frequency warping and a uniform filter bank, is developed. Detailed analyses of frequency warped signals are carried out. The effect of truncation of the original signal and the warped signal is investigated. It is shown that the reconstruction is near perfect and coding based on the new nonuniform filter bank is capable of noise shaping. A subband coder based on the nonuniform filter bank is constructed and results are presented. Objective assessment and informal subjective assessment are carried out and they show that the coding reaches high quality at 192 kbps per channel; however, some artefact is perceptable. An efficient implementation of the Koilpillai-Vaidyanathan pseudo-quadrature mirror filter (KVPQMF) bank, which features simplicity in prototype filter design and suitability for audio coding, is developed. The savings in the number of calculations and in the execution time over the direct implementation is significant.

In this thesis the development of a novel descriptor for boundary images represented in a chain code format is reported. This descriptor is based on a truncated series of orthogonal polynomials used to represent a piecewise continuous function derived from a chain code. This piecewise continuous function is generated from a chain code by mapping individual chain links onto real numbers. A variety of alternative mappings of chain links onto real numbers are evaluated, along with two specific orthogonal polynomials; namely Legendre polynomials and Chebychev polynomials. The performance of this series descriptor for chain codes is evaluated initially by applying it to the problem of locating short chains within a long chain; and then extending the application and critically evaluating the descriptor when attempting to match features from pairs of similar images. In addition, a formal algebra is developed that provides the rule base that enables the transformation and manipulation of chain encoded boundary images. The foundation of this algebra is based on the notion that the labelling of the directions of an 8-connected chain code is essentially arbitrary and 7 other, different and consistent labellings can be distinguished.

A novel antimicrobial dental composite system has been developed and evaluated.Both alumina and zirconia filler particles were covalently coated with an antibacterial resin and blended into a composite formulation, respectively. Surface hardness and bacterial viability were used to evaluate the coated alumina filler-modified composite.Compressive strength and bacterial viability were used to evaluate the coated zirconia filler-modified composite. Commercial composite Kerr was used as control. The specimens were conditioned in distilled water at 37°C for 24 h prior to testing. Four bacterial species Streptococcus mutans, Staphylococcus aureus, Pseudomon asaeruginosa and Escherichia coli were used to assess the bacterial viability. Effects of antibacterial moiety content, modified particle size and loading, and total filler content were investigated.<div><br><div>Chapter 2 describes how we studied and evaluated the composite modified with antibacterial resin-coated alumina fillers. The results showed that almost all the modified composites exhibited higher antibacterial activity along with improved surface hardness, as compared to unmodified one. Increasing antibacterial moiety content, particle size and loading, and total filler content generally increased surface hardness. Increasing antibacterial moiety, filler loading, and total filler content increased antibacterial activity. On the other hand, increasing particle size showed a negative impact on antibacterial activity. The leaching tests indicate that the modified experimental composite showed no leachable antibacterial component to bacteria.<br></div><div><br></div><div>Chapter 3 describes how we studied and evaluated the composite modified with antibacterial resin-coated zirconia fillers. The results showed that almost all the modified composites exhibited higher antibacterial activity along with decreased compressive strength, as compared to the unmodified control. It was found that with increasing antibacterial moiety content and modified filler loading, yield strength,modulus and compressive strength of the composite were decreased. In addition,the strengths of the composite were increased with increasing powder/liquid ratio.On the other hand, with increasing antibacterial moiety content, filler loading and powder/liquid ratio, antibacterial activity was enhanced.<br></div><div><br></div><div>In summary, we have developed a novel antibacterial dental composite system for improved dental restoratives. Both composites modified with the antibacterial resin-coated alumina and zirconia fillers have demonstrated significant antibacterial activities.The composite modified with the alumina fillers showed improved hardness values, but the composite modified with the zirconia fillers showed decreased compressive strength values. It appears that the developed system is a non-leaching antibacterial dental composite.<br></div></div>

Raloxifene is an FDA-approved selective estrogen receptor modulator (SERM) that improves tissue quality by binding to collagen and increasing the bound water content in the bone matrix in a cell-independent manner. In this thesis, active tissue formation was induced by non-invasive external tibial loading in female mice and combined with raloxifene treatment to assess their combined effect on bone morphology and mechanical properties. Thermoregulation is an important factor that could have physiological consequences on research outcomes, and was introduced as an additional experimental factor in this study. We hypothesized that by removing the mild cold stress under which normal lab animals are housed, a metabolic boost would allow for further architectural and mechanical improvements as a result of the combination of tibial loading and raloxifene treatment. Ten week old female C57BL/6J mice were treated with raloxifene, underwent tibial loading to a strain level of 2050με and were housed in thermoneutral conditions (32°C) for 6 weeks. We investigated bone morphology through microcomputed tomography (μCT) and mechanical properties via four-point bending and fracture toughness testing. Results indicated a combined improvement by external loading and raloxifene on geometry, particularly in the cancellous region of the bone, and also in bone mechanics leading to greater improvements than either treatment individually. Temperature did not have a robust impact on either bone architecture or mechanical integrity.

One of the most important advances in modern theoretical surface science and catalysis research has been the advent of Ab-Initio Density Functional Theory (DFT). Based on the electronic structure formulation of Pierre Hohenberg, Walter Kohn and Lu Jeu Sham, DFT has revolutionized theoretical research in heterogeneous catalysis, electrocatalysis, batteries, as well as homogeneous catalysis using first-principles electronic structure simulations. Combined with statistical mechanics, kinetic theory, and experimental inputs, DFT provides a powerful technique for investigating surface structure, reaction mechanisms, understanding underlying reactivity trends, and using them for rational and predictive design of materials for various catalytic chemistries, including those that can propel us towards a clean energy future – for example water gas shift (WGS), methanol synthesis, oxidation reactions, CO2 electroreduction, among many others. Fueled by advances in supercomputing facilities, numerous early and current DFT studies have been primarily focused on idealized simulations aimed at obtaining qualitative insights into experimental observations. However, as the immense potential of DFT has been unfolding, the demand for closer representation of realistic catalytic situations have rapidly emerged, and with it, the recognition of the need to reduce the disparity between theoretical DFT structures and real catalytic environments. Bridging this ‘materials gap’ necessitates using more rigorous catalyst structures in DFT calculations that can capture realistic experimental geometries, while at the same time, are creatively simplified to be computationally tractable. This thesis is a compilation of several projects on metals and metal/oxide systems that have been undertaken using DFT, in collaboration with experimental colleagues, with the goal of addressing some of the challenges in heterogeneous catalysis, while decreasing the ‘materials gap’ between theory and experiments.<div><br></div><div>The first several chapters of this thesis focus on bifunctional, metal/oxide systems. These systems are quintessential in numerous heterogeneous catalysis applications and have been the subject of extensive study. More interestingly, they sometimes exhibit synergistic enhancement in rates that is greater than the sum of the individual rates on the metal (on an inert support) or on the oxide in isolation. Such bifunctionality often stems from the modified properties at the nanoscale interface between the metal and the oxide and is an active field of research. In particular, while a large body of literature exists that investigates the activity of metals, the role of the support in bifunctional systems is often uncertain and is the subject of investigation of the first few chapters of this thesis. We chose to study WGS on Au as support effects are particularly prominent on this system. The second chapter examines WGS on Au/ZnO, where realistic catalytic environment at the interface is reproduced by analyzing the thermodynamics of surface hydroxylation of the oxide under reaction conditions, and its effect on WGS kinetics is quantified through a microkinetic analysis. This study highlights the importance of considering spectator species which can drastically influence the energetics and kinetics of a reaction at a metal/oxide interface. In addition, fundamental aspects of the effect of surface hydroxyls on the electronic structure at the interface is also discussed.<br></div><div><br></div><div>The third chapter of the thesis builds on this theme and analyzes the effect of systematic perturbation of electronic structure at the interface through substitutional doping of the oxide. Chapters 3 and 4 focus on Au/MgO, a system which has been previously studied in extensive detail in our group and benchmarked through experiments. The effects of a series of dopants of varying electronic valences have been analyzed on a number of properties at the interface – vacancy formation energies, adsorption energies of intermediates, scaling properties, activation energy barriers and so on. Exciting new scaling relationships are identified at this interface, having properties different from that observed on extended surfaces, and are interpreted using an electrostatic model. In the subsequent chapter, we identified Bronsted-Evans-Polanyi relationships for the different steps in the WGS pathway for a series of dopants. Coupled with the scaling relations, these trends were then used in conjunction with a dual-site microkinetic model to perform a volcano analysis for interfacial rates. Our analysis thus builds, for the first time, a rational design paradigm for electronic structure perturbation of the support at a bifunctional interface. The next chapter further investigates support effects, both geometric and electronic, in greater detail for Au supported on a series of oxide supports and discusses accelerated identification of an activity descriptor through a close fusion between computations and experiments.<br></div><div><br></div><div>In addition to interfacial effects of the support, this thesis also briefly examines a more apparent role of the oxide, wherein it influences the geometry of the supported metal. Two different Au-based systems are investigated using surface science approaches in Chapter 6 - the segregation properties of a bimetallic Au/Ir alloy on anatase and wetting behavior of Au-FexOy heterodimers – both of which are representative of the structural evolution of a supported catalyst under reaction conditions. Through our analysis, we show that the oxide directly influences these behaviors of the supported metal.<br></div><div><br></div><div>The next few chapters explore catalysis using metallic systems, focusing on transition metals, an important class of materials in heterogeneous catalysis and constitutes the major body of DFT literature for trend based catalytic analyses. A crucial factor that contributed to the success of such high-throughput screening studies was identification of linear scaling relationships on transition metals, whereby the adsorption energy of complex molecular fragments was linearly related to that of simple atomic adsorbates. However, while these relationships are valid for low adsorbate coverages, at higher, catalytically relevant coverages, deviations from linearity are common, thus presenting a materials gap in volcano analyses. The incorporation of coverage effects, therefore, in scaling relations has been a pressing challenge. This thesis describes a simple means of systematically capturing changes in reaction energies due to coverage effects through a pairwise interaction model, where the changes in adsorption energies are shown to be a direct function of the number of neighbors and interaction parameters determined through DFT. In addition, we also draw a mathematical correspondence between scaling relations at high coverage and that at low coverage and discuss its implications on the existence of linear scaling relations.<br></div><div><br></div><div>In Chapter 8, we discuss collaborative work on Pt based catalysts, an active catalyst for many chemical and electrochemical systems. We explore trends in WGS on bimetallic Pt-M systems and identify an activity descriptor by correlating experimental rates with the binding strength of OH* on model surfaces of bimetallic alloys. In addition, we also investigate the interaction between Na promoter and Pt under reaction conditions, using an inverse oxide model, to obtain insights into the nature of promotion of alkali metals on WGS on Pt catalysts.<br></div>

<p>Development of durable icephobic coating and reduction of ice accumulation on the product surfaces has proven to be a challenging task in the past decade. Considering the challenges posted during ice storms and existing limitations to the state of the art, development of durable icephobic coating which can provide low ice adhesion strength and less ice weight increase is a critical milestone for industries and research communities. To obtain durable icephobic coating, high temperature and weather resistance Fluoro-Ethylene-Alkyl-Vinyl-Ether (FEVE) binder was selected to design a smooth and superhydrophobic coatings. These coatings were benchmarked against commercially available silicone epoxy and superhydrophobic coatings and validated its surface roughness, surface wettability and icephobic performance such as ice adhesion strength and ice accumulation. To evaluate coatings thermal durability, targeting power transmission line application, these coatings were exposed to extreme thermal ageing conditions (200 ^oC for 60 days) and retention of icephobic performance were measured. Though, commercial coatings have provided better icephobicity at unaged condition, after high temperature heat ageing these coatings icephobic performance were deteriorated significantly. However, FEVE based coating had retained its surface characteristics and icephobic properties after aggressive thermal ageing.</p>

<p>Land use constraints have motivated investigation into the spatial coexistence of solar photovoltaic electricity production and agricultural production. Previous work suggests that agriculture-photovoltaic (agrivoltaic) systems either decrease crop yield or are limited to shade-tolerant crops. Existing experimental work has also emphasized fixed south-facing configurations with traditional commercial panel shapes, and modeling work is sparse. In this work, the effects of different photovoltaic array configurations and panel designs on field insolation spatial and temporal variation are explored in detail to determine photovoltaic design routes that may increase expected crop yield in agrivoltaic systems. It is found that photovoltaic row orientation is the most influential factor on insolation homogeneity due to shadow migration paths. Additionally, it is shown that utilization of mini-modules in patterned panel designs may create more optimal conditions for plant growth while using the same area of PV, thus improving the land efficiency ratio of the agrivoltaic system. Different solar tracking algorithms are explored to optimize the trade-off between electricity production and expected crop growth. The feasibility of select agrivoltaic systems is explored for multiple U.S. locations. This thesis concludes with recommendations for photovoltaic system designs corresponding with specific crop growth considerations.<br></p>

<p>Pavement macrotexture contributes greatly to road surface friction, which in turn plays a significant role in reducing road incidents. Conventional methods for macrotexture measurement techniques (e.g., the sand patch method, the outflow method, and laser measuring) are either expensive, time-consuming, or of poor repeatability. This thesis aims to develop and evaluate affordable and convenient alternative approaches to determine pavement macrotexture. The proposed solution is based on multi-view smartphone images collected in situ over the pavement. Computer vision techniques are then applied to create high resolution three-dimensional (3D) models of the pavement. The thesis develops the analytics to determine two primary macrotexture metrics: mean profile depth and aggregation loss. Experiments with 790 images over 25 spots of three State Roads and 6 spots of the INDOT test site demonstrated that the image-based method can yield reliable results comparable to conventional laser texture scanner results. Moreover, based on experiments with 280 images over 7 sample plates with different aggregate loss percentage, the newly developed analytics were proven to enable estimation of the aggregation loss, which is largely compromised in the laser scanning technique and conventional MPD calculation approach. The root mean square height based on the captured images was verified in this thesis as a more comprehensive metric for macrotexture evaluation. It is expected that the developed approach and analytics can be adopted for practical use at a large scale. </p>