<p dir="ltr">Accurately locating a radio-frequency (RF) emitter is imperative in the defense sector, and passive direction finding systems are intriguing due to relatively low cost. This approach involves using the time difference between a signal’s impact at equispaced antennas to determine the location of the emitter, a particular challenge for wideband waveforms operating near the noise floor. Microwave photonic systems have been demonstrated for passive direction finding. These techniques possessed drawbacks, such as reliance on the incoming signal’s bandwidth, dependence on laser power, or the inability to recover an angle from wideband pulses. This thesis presents a novel approach to passive direction finding by translating the methods of spectral interferometry from the optical domain to RF. Spectral interferometry involves interfering a time-delayed reference pulse with a “signal” pulse that has passed through an unknown system. By removing the spectral phase of the reference pulse from the resulting interferogram, the spectral phase of the uncharacterized system is recovered. This enables direction-finding for many waveforms, including the wideband low peak power chirps frequently used in radar. Incorporating an analog optical delay line into both a hard-wired RF interferometer and a two-element antenna array demonstrated spectral interferometric processing of chirped signals with up to 1 GHz instantaneous bandwidth. The technique extracted accurate delays and angles to within 2$\degree$ throughout testing. This approach only requires the imposed delay be longer than the autocorrelation of the bandwidth limited pulses. With additional backend processing, this method could simultaneously determine the angle and classify the incoming signal.</p>

<p dir="ltr">Acoustic holography is a powerful tool in the visualization of sound fields and sound sources. It provides engineers and researchers clear insights into sound fields as well as their sound sources. Some widely-used methods include Nearfield Acoustical Holography (NAH), Statistically Optimized Nearfield Acoustic Holography (SONAH) and the Equivalent Source Method (ESM). SONAH and ESM were developed specifically to tackle the intrinsic deficiency of the Fourier-based NAH which requires that the sound field fall to negligible levels at the edges of the measurement aperture, a requirement rarely met in practice. Besides the aforementioned methods, the Inverse Boundary Element Method (IBEM) can be used, given sufficient measurements and computational resources. As useful as they are in visualizing the sound field, none of these methods can provide direct guidance on potential design modifications of the observed structure in order to unequivocally reduce sound power radiation. Acoustic radiation mode analysis has previously been primarily associated with active noise control applications. Since the radiation modes radiate sound power independently, it is only necessary to modify the surface vibration patterns so that they do not couple well with the radiation modes in order to guarantee a reduction of the radiated sound power. Since the radiation modes are orthogonal and complete, they can be used as the basis functions through which the source surface vibration can be described. Therefore, an acoustic holography method based on the acoustic radiation modes will enable the sound power ranking of the modal components of the surface vibration pattern, and in turn, point out the component(s) which should be targeted in order to reduce the overall sound power. However, use of the acoustic radiation modes in the inverse procedure comes with a price: the detailed geometry of the object to be measured must be obtained, thus enabling the calculation of acoustic radiation modes and the modal pressures. But this is not an issue for original equipment manufacturers given that almost all prototypes are now designed with CAD, as is the case with the engine example to be described next.</p><p dir="ltr">In modern engine design, downsizing and reducing weight while still providing an increased amount of power has been a general trend in recent decades. Traditionally, an engine design with superior NVH performance usually comes with a heavier, thus sturdier structure. Therefore, modern engine design requires that NVH be considered in the very early design stage to avoid modifications of engine structures at the last minute, when very few changes can be made. NVH design optimization of engine components has become more practical due to the development of computer software and hardware. However, there is still a need for smarter algorithms to draw a direct relationship between the design and the radiated sound power. At the moment, techniques based on modal acoustic transfer vectors (MATVs) have gained popularity in design optimization for their good performance in sound pressure prediction. Since MATVs are derived based on structural modes, they are not independent with respect to radiated sound power. In contrast, as noted, acoustic radiation modes are an orthogonal set of velocity distributions on the structure’s surface that contribute to the radiated sound power independently. As a result, it is beneficial to describe structural vibration in terms of acoustic radiation modes in order to identify the velocity distributions that contribute the majority of the radiated sound power. Measures can then be taken to modify the identified vibration patterns to reduce their magnitudes, which will in turn result in an unequivocal reduction of the radiated sound power. A workflow of the structural optimization procedure is proposed in this dissertation.</p><p dir="ltr">While acoustic radiation modes have great efficiencies in describing radiated acoustic power, the computation of acoustic radiation modes can be time consuming. In the last chapter of this thesis, a novel way of calculating acoustic radiation modes is proposed, which differs from the traditional singular value decomposition of the power radiation resistance matrix, and which is more efficient than previously proposed procedures. </p><p><br></p>

<p dir="ltr"><a href="" target="_blank">ABSTRACT</a></p><p dir="ltr">This dissertation delves into postmodern wordless picture books, employing a multimodal content analysis across twenty-eight titles. It stands on a theoretical framework amalgamating concepts from multimodality grounded in social semiotics, critical literacy, and postmodernism. Among the corpus, three titles— <i>Alien Nation</i> (Bassi, 2021), and <i>The Rabbits</i> (Tan, 1998) and <i>The Other Side</i><i> </i>(Bányai, 2005)— emerge as principal subjects of analysis, with the remaining twenty-five titles providing contextual support. Guiding this journey is Barthes' (1977) tripartite model of visual textual meaning at the literal, symbolic, and personal levels, illuminating the intricate layers of the analyzed picture books.</p><p dir="ltr">The analysis unveils distinguishing features of these books: 1) Disruption of boundaries of story worlds and reality; 2) Disruption of space and/or time; 3) Multiple levels of intertextuality; 4) Visual incongruity, visual metaphor and 5) Personal Narratives. Such characteristics are found to challenge narrative conventions, blur reality-fiction distinctions, and implore readers to cultivate personal narratives and critical interpretations.</p><p dir="ltr">However, the research's significance extends beyond feature identification. It births a postmodern literacy pedagogy that encompasses visual, critical, and postmodern dimensions. This pedagogy advocates for embedding postmodern wordless picture books in pre-service teacher curricula. The aim surpasses genre acquaintance, aspiring for a profound grasp of the books' visual nuances and ideological layers. As these visual dynamics play a pivotal role in shaping a reader's experience, they bolster critical reading and foster personal and emotive connections to narratives. By engaging with such books, pre-service teachers gain multifaceted insights into intricate social and historical issues. They're empowered to question prevailing narratives, embrace diverse perspectives, and champion social justice and educational equity. Viewed through this prism, postmodern wordless picture books serve as powerful tools, guiding future educators to see the world from diverse perspectives, navigate uncertainties, foster empathy, and empower varied voices, ultimately becoming advocates for change and inclusion.</p>

<p dir="ltr">The demand for sustainable and renewable energy sources has prompted significant research and development efforts in the field of biomass gasification. Biomass gasification technology holds significant promise for sustainable energy production, offering a renewable alternative to fossil fuels while mitigating environmental impact. This thesis presents a detailed study on the design, development, and implementation of a Plug-Flow Reactor Biomass Gasifier integrated with an Automated Auger Jam Detection System and a Blower Algorithm to maintain constant reactor pressure by varying blower speed with respect to changes in reactor pressure. The system is based on indirectly- heated pyrolytic gasification technology and is developed using Simulink™.</p><p dir="ltr">The proposed gasification system use the principles of pyrolysis and gasification to convert biomass feedstock into syngas efficiently. An innovative plug-flow reactor configuration ensures uniform heat distribution and residence time, optimizing gasification performance and product quality. Additionally, the system incorporates an automated auger jam detection system, which utilizes sensor data to detect and mitigate auger jams in real-time, thereby enhancing operational reliability and efficiency. By monitoring these parameters, the system detects deviations from normal operating conditions indicative of auger jams and initiates corrective actions automatically. The detection algorithm is trained using test cases and validated through detailed testing to ensure accurate and reliable performance.</p><p dir="ltr">The MATLAB™-based implementation offers flexibility, scalability, and ease of integration with existing gasifier control systems. The graphical user interface (GUI) provides operators with real-time monitoring and visualization of system status, auger performance, and detected jam events. Additionally, the system generates alerts and notifications to inform operators of detected jams, enabling timely intervention and preventive maintenance. </p><p dir="ltr">To maintain consistent gasification conditions, a blower algorithm is developed to regulate airflow and maintain constant reactor pressure within the gasifier. The blower algorithm dynamically adjusts blower speed based on feedback from differential pressure sensors, ensuring optimal gasification performance under varying operating conditions. The integration of the blower algorithm into the gasification system contributes to stable syngas production and improved process control. The development of the Plug-Flow Reactor Biomass Gasifier, Automated Auger Jam Detection System, and Blower Algorithm is accompanied by rigorous simulation studies and experimental validation.</p><p dir="ltr">Overall, this thesis contributes to the advancement of biomass gasification technology by presenting a detailed study on a plug flow reactor biomass gasifier with indirectly- heated pyrolytic gasification technology with an Automated Auger Jam Detection System and Blower Algorithm. The findings offer valuable insights for researchers, engineers, policymakers, and industry stakeholders supporting the transition towards cleaner and more renewable energy systems.</p>

<p dir="ltr">Lithium-ion (Li-ion) batteries are promising electrochemical energy storage and conversion systems to drive the rechargeable world toward a sustainable future. Following the breakthrough of material innovations, advanced Li-ion batteries have significantly mitigated the range and lifetime anxieties of electric vehicles (EVs) and consumer electronics. Nevertheless, state-of-the-art Li-ion chemistries still suffer from several defects, such as rapid degradations under abusive or fast-charge scenarios and unfavorable high thermal instabilities. Essentially, aging mechanisms and safety hazards of Li-ion cells are strongly coupled events. The cell safety factors are most likely to be deteriorated as degradation progresses, making the cell less safe after a long-term deployment. In this thesis, we comprehensively investigate thermo-electrochemical interactions on the safety of Li-ion batteries. Fundamental principles of Li-ion batteries, basic knowledge about material-level thermal instabilities at electrode-electrolyte interphases, thermal characterization approaches, and thermal runaway mechanisms under abusive scenarios are fully overviewed. Thermally unstable characteristics of key cell components, including inter-electrode crosstalk as a result of oxygen liberation from cathode lattice structures, significant electric energy release from massive internal short circuit due to separator collapse, anode-centric lithium-plating-induced early exotherm, and silicon-dopant-driven thermal risks of composite anodes, are specifically discussed to understand their critical role in accelerating cell-level thermal runaway catastrophes. Aging pathways of Li-ion cells under off-normal conditions, particularly overdischarge and fast charging, are thoroughly elucidated using a promising reference electrode architecture, which effectively deconvolutes the electrode behaviors from the complex full-cell performance for precise identification of the root causes in cell failure. Given the profound revelation of degradation-safety sophistication in various Li-ion chemistries, corresponding mitigation and prevention strategies are proposed to maximize cell lifetime and reliability. This thesis provides new insights into aging and safety diagnostics of cutting-edge Li-ion batteries, taking one step further in the online monitoring of battery state of health to develop adaptive battery management systems.</p>

<div>Shifts in the human diet to more refined foods and ingredients have contributed to the rise in metabolic disease rates associated with long-term consumption of foods causing swift rises in blood glucose response. Foods which result in a more moderate blood glucose curve are considered healthier by increasing satiety and reducing oxidative stress. Sorghum products contain naturally slowly digested starch. The matrix of sorghum porridges contains kafirin protein bodies which cross link around gelatinizing starch molecules, while similar nascent matrices in other cereals aggregate and collapse. The 3-deoxyanthocyanidin pigments unique to sorghum may be accountable for the difference in matrix stability. The density of the starch entrapped in the matrices is thought to partially inhibit α-amylase access to the starch, reducing overall starch digestion and thereby mitigating glucose response. The purpose of this work was to increase our understanding of how phenolic compounds in sorghum interact with endosperm proteins to create a stable matrix, and to explore if the knowledge might be translated to other starchy cereal products. In the first study, phenolic extracts from flours (sorghum, corn masa, white rice) were characterized for phenolic content, antioxidant activity, phenolic components, and their ability to interact with a model protein system (ovalbumin) in order to examine protein polymerization. In the second study, specific phenolic compounds in sorghums (<i>p</i>-coumaric, sinapic, and gallic acids; (+)-catechin; and apigeninidin, a 3-deoxyanthocyanidin found in sorghums) were interacted in the model protein system at different concentrations to observe extent and type of protein polymerization, and promising compounds subjected to fluorescence quenching spectroscopy to examine the nature of the interactions. The final study explored the effects of apigeninidin addition to a yellow corn flour and naturally present anthocyanin (blue corn) on starch digestion and microstructure of porridges by utilizing an <i>in vitro</i> α-amylase assay and confocal microscopy. </div><div>The slow digestion of starch in cooked sorghum products can be attributed to the 3-deoxyanthocyanidin compounds present in the grain participating in sulfhydryl-disulfide interchanges which results in extensive kafirin cross-linking surrounding starch granules. While other phenolic and redox-active components may affect matrix formation and stability, 3-deoxyanthocyanidins appear to have the most direct influence, and their ability to modify food protein matrices appears to have a direct result on starch digestion <i>in vitro</i>.</div>

The Keap1-Nrf2 pathway regulates a wide range of cytoprotective genes, and has been found to serve a protective and beneficial role in many body systems. There is limited information available, however, about its role in bone homeostasis. While Nrf2 activation has been suggested as an effective method of increasing bone mass and quality, there have been conflicting reports which associate Keap1 deficiency with detrimental phenotypes. As Keap1 deletion is a common method of Nrf2 activation, further study should address the impacts of various methods of regulating Nrf2 expression. Also, little research has been conducted on the specific pathways by which Nrf2 activation improves bone quality. In this study, the effects of alterations to Nrf2 activation levels were explored in two specific and varied scenarios. In the first experiment, moderate Nrf2 activation was achieved via partial deletion of its sequestering protein, Keap1, in an aging mouse model. The hypothesis tested here is that moderate Nrf2 activation improves bone quality by affecting bone metabolism and response to mechanical loading. The results of this first experiment suggest a subtle, sex-specific effect of moderate Nrf2 activation in aging mice which improves specific indices of bone quality to varying degrees, but does not affect loading-induced bone formation. It is likely that the overwhelming phenotypic impacts associated with aging or the systemic effects of global Keap1 deficiency may increase the difficulty in parsing out significant effects that can be attributed solely to Nrf2 activation. In the second experiment, a cell-specific knockout of Nrf2 in the osteocytes was achieved using a Cre/Lox breeding system. The hypothesis tested here is that osteocyte-specific deletion of Nrf2 impairs bone quality by affecting bone metabolism and response to mechanical loading. The results of this experiment suggest an important role of Nrf2 in osteocyte function which improves certain indices of bone quality, which impacts male and female bones in different 7 ways, but did not significantly impact loading-induced bone formation. Further studies should modify the method of Nrf2 activation in an effort to refine the animal model, allowing the effects of Nrf2 to be isolated from the potential systemic effects of Keap1 deletion. Future studies should also utilize other conditional knockout models to elucidate the effects of Nrf2 in other specific cell types.

<div>Due to the instabilities that may occur in dc power systems with regulated power electronic loads such as those used in aircraft, ships, as well as terrestrial vehicles, many analysis techniques and design methodologies have been developed to ensure stable operation following small disturbances starting from normal operating conditions. However, these techniques do not necessarily guarantee large-displacement</div><div>stability following major disturbances such as faults, regenerative operation, pulsed loads, and/or loss of generating capacity. In this thesis, a formal mathematical definition of large-displacement stability is described and the analytical conditions needed to guarantee large-displacement stability are investigated for a notional dc power system. It is shown possible to guarantee large-displacement stability for any piecewise continuous value of load power provided it is bounded by the peak rating of the dc source.</div>

Combustion research is at the forefront of development of clean and efficient IC engines, gas turbines, rocket propulsion systems etc. With the advent of faster computers and parallel programming, computational studies of turbulent combustion is increasing rapidly. Many turbulent combustion models have been previously developed based on certain underlying assumptions. One of the major assumptions of the models is the regime it can be used for: either premixed or non-premixed combustion. However in reality, combustion systems are multi-regime in nature, i.e.,\ co-existence of premixed and non-premixed modes. Thus, there is a need for development of multi-regime combustion models which closely follows the physics of combustion phenomena. Much of previous modeling efforts for multi-regime combustion was done using flamelet-type models. As a first, the current study uses the highly robust transported Probability Density Function (PDF) method coupled with Large Eddy Simulation (LES) to develop a multi-regime model. The model performance is tested for Sydney Flame L, a piloted methane-air turbulent flame. The concept of flame index is used to detect the extent of premixed and non-premixed combustion modes. The drawbacks of using the traditional flame index definition in the context of PDF method are identified. Necessary refinements to this definition, which are based on the species gradient magnitudes, are proposed for the multi-regime model development. This results in identifying a new model parameter beta which defines a gradient threshold for the calculation of flame index. A parametric study is done to determine a suitable value for beta, using which the multi-regime model performance is assessed for Flame L by comparing it against the widely used non-premixed PDF model for three mixing models: Modified Curl (MCurl), Interaction by Exchange with Mean (IEM) and Euclidean Minimum Spanning Trees (EMST). The multi-regime model shows a significant improvement in prediction of mean scalar quantities compared to the non-premixed PDF model when MCurl mixing model is used. Similar improvements are observed in the multi-regime model when IEM and EMST mixing models are used. The results show potential foundation for further multi-regime model development using PDF model.

<p>In order to comfortably and effectively function in U.S. classrooms, both international students and domestic students benefit from the development of interactive and intercultural communication skills. At Purdue University, a large, public, R1 institution with a substantial international population, the internationalization of the student body is a priority. To examine the relationship between academic and social integration of international and domestic students on campus, international (ESL) undergraduate students (L2 English, n=253) from the Purdue Language and Cultural Exchange Program (PLaCE), and domestic undergraduate students (L1 English n=50) from the first-year composition program (ICaP), participated in a voluntary survey. The framework for investigating students’ interaction with peers and teachers was derived from Severiens and Wolff (2008). Four aspects of new, incoming students’ adaptation (Global Perspective, Intercultural Competence, Acculturation Mode, and Willingness to Communicate) were addressed by the survey. Although there were similarities between international and domestic students, the results revealed international students had more opportunities to interact with peers from diverse language backgrounds in formal academic contexts, including classroom activities, peer-group work in first-year programs and language programs. However, in informal, social contexts, neither international nor domestic students took advantage of opportunities to interact with each other. The tendency to prefer social interactions with co-nationals may contribute to social isolation and limited integration of international and domestic students within broader social contexts outside of classrooms. Yet, rather than resisting this trend, instructors and administrators might enhance opportunities for interaction in academic contexts where both groups are most willing to participate. Findings from this study can contribute to the development of first-year programs that provide realistic solutions for the enhanced internationalization of both domestic and international students on campus. </p>