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“Rude, Misshapen, Monstrous Rabblement”: Race, Disability, and Gender in Early Modern England
No full textMy first chapter, “‘Ugly Monstrous Shapes’: Reading Signs of Alterity,” looks at presentations of “othered” female bodies in Book I of Edmund Spenser’s The Faerie Queene. This chapter draws our attention to various old, deformed, or otherwise dysfunctional bodies. In doing so, it not only emphasizes the necessity for reading but also listening to the “ugly monstrous shapes, that elsewhere no man may” find. Drawing attention to metaphor, rhyme, and non-verbal sounds produced by the disabled/disabling bodies in the poem, this chapter locates Spenser’s racialization of bodies in his careful cultivation of sympathy. By using sound as a disability structure, my reading depicts the importance of affect in the amplification of humoral, racial, and physiological difference—especially in the context of English and Irish bodies. This chapter argues that the poem not only offers a way for its idealized reader(s) to hear and to repent their own emotional shortcomings within a Protestant system, but in doing so, to regulate their own bodily and affective responses to alterity. The idea of bodily and affective responses to alterity is central to my reading of Titus Andronicus in the next chapter. In this second chapter, “‘Aaron will have his soul black like his face’: Annotating Disabled Masculinity in Titus Andronicus,” I argue that Shakespeare’s staging of pain, exclusion, and alterity draws on dominant emotional scripts. In my reading, emotions demonstrate the intersections between race, genre, and disability in Elizabethan revenge tragedy. I demonstrate how, in this play, the capacity/incapacity to hear and to repent becomes essential to the deployment of racial and disability markers. I argue that the play’s manipulation of suffering and sympathetic identification not only depicts processes of racial trauma, but it also allows that trauma—especially the trauma experienced or anticipated by the black body—to empower its audience. In other words, my work on Titus Andronicus hinges upon the racialization of compassion and pity through the “dysgraphia of anti-blackness,” to borrow Christina Sharpe’s terminology. The concern with emotional solidarities reappears in my third chapter in a slightly modified form in terms of the aesthetics of care. In this chapter entitled, “What Strange New Motions Do I Feel: Love’s Cure, the Ethics of Care, and the Performance of Normalcy”, I attempt a reading of transness through the play’s anxiety over gender dysphoria, appetitive desires, and the “cure” for non-normativity. My reading hinges on three main ideas: a reading of gender not with but as disability, the racialization of desire, and the notion of “strange”-ness (used in the play to describe heteronormative rather than transgressive desire). This is a relatively understudied play from the period, despite being attributed to major playwrights, and to my knowledge, critics have yet to engage with the play’s remarkable racial moments or its use of disability aesthetics. Yet, this play has so much to offer in its incredibly rich description of feminine care, masculine “ability”, and the dichotomy between “habits” and “customs”. My chapter, therefore, attempts to make visible the performances of “normalcy” while juxtaposing it with experiences of trans-maladjustment, suggesting that where the habitual body is the gender non-conforming one, to “cure” its symptoms can be just as unnatural. The impulse to pathologize different bodyminds and mark them as “unnatural” remains an important tenet in Middleton’s The Revenger’s Tragedy, the subject of my final chapter. This chapter, “‘Black, Wicked, and Unnatural:’ Locating Monstrosity in Middleton’s Works,” demonstrates the confusion of identities that permeates Middleton’s play and England more generally in this time. Looking at presentations of deformed, speckled, and ethnically othered bodyminds, this chapter complicates notions of moral and physical deviation by interrogating its overreliance on infectious blackness. Exploring scripts of monstrosity, this chapter tries to isolate the race-making and disability rhetoric that informs Middleton’s works. It asks, with Middleton, what it means to be “black enough” in the premodern world by exploring the indelible markers of blood and ink in relation to the “monstrous” body. My reading thus explores the play’s investment in orienting the standardized body and depicting the audience’s complicity in constructions of a normative national identity that simultaneously co-opts Italian vengefulness, and at the same time, distinguishes it from more laudable English abilities
Fate, Composition and Formation of Unknown N-Nitrosamines in Wastewater and Wastewater-Impacted Waters
No full textN-Nitrosamines form as byproducts during oxidative water treatment or occur as impurities in consumer and industrial products. N-Nitrosamines and their precursors pose significant concerns for water utilities exploiting wastewater-impacted water supplies, as many N-nitrosamines are potential human carcinogens and have genotoxicity. To date, research on N-nitrosamines in environmental engineering has primarily focused on the occurrence, sources, formation, and control of N-nitrosodimethylamine (NDMA) in the broad context of drinking water and wastewater treatment. However, NDMA and the few other N-nitrosamines of current interest only constitute a fraction of the larger pool of total N-nitrosamines (TONO) in source waters and wastewater, while the rest of N-nitrosamines in the TONO pool remains largely unidentified. Even less is known about the origins, fate, and toxicological relevance of these uncharacterized N-nitrosamines. In the first study (Chapter 2), I compared the performance of acidic triiodide-based chemiluminescence method (HI3-CL) and ultraviolet photolysis-based chemiluminescence (UV-CL) method for TONO measurements in wastewater samples. Sixty-six N-nitroso compounds showed varied conversion efficiencies relative to NDMA with both chemiluminescence methods. On average, TONO levels in raw and chloraminated wastewater samples measured by the HI3-CL method were 2.1 ± 1.1 times those measured by the UV-CL method, suggesting potential matrix interferences for denitrosation by UV photolysis as further confirmed by spike recovery tests. This comparison addressed methodological gaps in TONO analysis, highlighted several practical considerations when implementing the HI3-CL and UV-CL methods for TONO analysis in wastewater, and validated an experimental platform for subsequent chapters. In the second study (Chapter 3), I developed an integrated analytical workflow combining solid phase extraction, TONO analysis, and liquid chromatography-high-resolution mass spectrometry (LC-HRMS) for systematic quantification and nontarget screening of N-nitrosamines in wastewater samples. A scoring scheme named TONO response factor was developed to enable a quantitative comparison between TONO and specific N-nitrosamine concentrations and was applied to refine the compositional analysis of TONO reported by the literature. To address gaps regarding the fate of TONO components in conventional wastewater treatment plants (WWTPs), the concentrations of specific N-nitrosamines and TONO in samples collected along the treatment trains of eight full-scale facilities in New York were consolidated by treatment steps for comparative analysis. Nontarget screening of raw and chloraminated samples from these facilities also led to the identification and confirmation of additional N-nitrosamines beyond commonly detected species such as NDMA. Of these newly identified N-nitrosamines, one was the N-nitroso derivative of a secondary amine-containing pharmaceutical – desloratadine, which was further evaluated in Chapter 4. Complementary measurements of wastewater samples using fluorescence spectroscopy, on the other hand, provided initial evidence for the proteinaceous nature of uncharacterized TONO precursors. This work provided information on the fate of TONO and their precursors in conventional WWTPs with varying treatment configurations and provided new insights into the possible identities of precursors to uncharacterized TONO components. In the third study (Chapter 4), I evaluated the formation of N-nitroso derivatives upon chloramination using non-labeled and 15N-labeled preformed monochloramine on 17 secondary amine-containing pharmaceuticals commonly detected in wastewater. LC-HRMS identified nine N-nitroso derivatives predicted to form via nitrosation of their secondary amine moieties, with reference to custom-synthesized standards. Chloramination of nine secondary-amine pharmaceuticals led to the formation of corresponding N-nitroso derivatives, confirmed by data dependent-MS2 spectra. The formation of N-nitroso derivatives was inhibited by radical scavengers or in the absence of dissolved oxygen, suggesting the involvement of radical intermediates and molecular oxygen. Hypothesized formation pathways were then proposed based on the detection of reaction intermediates on LC-HRMS. Molar yields of N-nitrosation reaction mixtures determined via chemiluminescence detection were higher than those measured by LC-HRMS, possibly due to the contribution from other N-nitrosamines. This work provided insight into an overlooked formation pathway of N-nitroso derivatives from secondary amine containing pharmaceuticals
Between Visits: Hindu Domestic Religiosity, Home Shrines, and Thirdspace in the Diaspora
No full textThis dissertation analyzes the importance of the domestic sphere as a site for the transmission and development of an individual devotional disposition for Swaminarayan Hindus living in the United States and Canada. Focusing on Hindus in the Bochasanwasi Akshar Purushottam Swaminarayan Sanstha (BAPS) community living in Canada and the United States, this dissertation presents a new direction for existing scholarship of Hinduism in the public sphere by arguing for a more holistic study of how Hindus living outside of India develop and maintain a religious identity in their daily lives in the domestic sphere, both collectively as a family and individually. This dissertation explores home shrines and the religious praxis surrounding them, devotees’ collective and individual forms of engagement with various acts of bhakti (devotion), and how BAPS fostered community through varied uses of technology during the COVID19 pandemic. In analyzing the domestic sphere through the analytical lens of spatial theory, I demonstrate the role the domestic sphere carries in devotees’ sādhanā (spiritual endeavors) and overall negotiation of identity as a bhakta (devotee)
PULLING UP THE TANGLED ROOTS OF RURAL NOSTALGIA: A RHETORICAL STUDY OF STORY AND SPACE, NATURE AND NATION
Get PDFDrawing from queer and feminist methodologies, Pulling Up the Tangled Roots of Rural Nostalgia engages rhetorical analysis of popular culture texts, specifically the film The Power of the Dog (2021) and television shows Schitt’s Creek (2015-2020) and Reservation Dogs (2021- ), and material spaces, specifically Yellowstone National Park, to develop a framework for tracing how particular constructions of rural nostalgia (such as “the small town,” “the frontier,” “the cowboy,” “the Indian Other,” “the wilderness”) circulate back and forth across widely consumed digital texts, collective imaginaries, political structures, and material spaces. As my dissertation pulls up and examines the tangled roots of rural nostalgia—roots that take us to the very origin stories on which the nation was built—I ask who is invested in nostalgic narratives of rurality, why, and to what ends. In conjunction, I map the ways rural nostalgia and its rhetorical constructions (such as “the cowboy,” “the noble savage,” and “the hick”) contribute to the composition of our social and political realities—from land use and management to the intersectional structures of gender, race, and class. Further, I ask what pedagogical possibilities we might find modeled in contemporary popular culture texts and in the composition of rural spaces. What might we—as researchers, writing instructors, and community members—learn about deploying rhetorical and narrative tactics in ways that revise our deepest, and most divisive, stories? Ultimately, this work contributes to conversations across rural, narrative, queer, feminist, settler colonial, and rhetoric and composition studies; proposes new ways of understanding and responding to the past times, places, and ways of life that rhetorics of rural nostalgia attempt to bring into the future; and perhaps most urgently, points to possibilities for suturing harmful divides across rural, urban, and suburban communities
AN INVESTIGATION OF THE PROCESSES OF TEACHERS\u27 DECISIONS TO CHOOSE AND SEQUENCE EXAMPLES IN THE TEACHING AND LEARNING OF MATHEMATICS
No full textAbstract This study aimed to investigate secondary mathematics teachers’ decision-making process and the influences of their decision-making as they planned and implemented instructions. Previous studies on teachers\u27 use of curriculum materials have focused on the general interaction with the curriculum. The literature also indicates that curriculum materials significantly influence what mathematics content teachers cover and how they teach it (Drake & Sherin, 2006; Remillard & Byrans, 2004). Such materials include examples that, in mathematics teaching, play a vital role in developing mathematical concepts and procedures (Bills & Watson, 2008; Zodik & Zaslavsky, 2008). This literature has reported a limited understanding of how and why secondary mathematics teachers decide to follow, adapt, or omit examples from curriculum materials and sequence them in instruction. This understanding can provide insights into teachers\u27 education programs, curriculum designers, and mathematics teachers. With those issues in mind, this study was designed to investigate the following questions: 1) How do teachers make decisions to follow, adapt, or omit examples and activities when planning their lessons? 2) Why do teachers decide to follow, adapt, or omit examples from curriculum materials? Participants were four mathematics teachers in the U.S. who teach in grades 7–12 and were using curricula that were new to them. This study employed a multiple case study research design to investigate the process and influences of mathematics teachers\u27 decision-making. Data were collected using multiple sources, including survey responses, semi-structured teachers\u27 decision-making, and artifacts created by the teachers. The data were analyzed mainly using thematic analysis (inductive and deductive methods) to identify emerging patterns. Results showed that teachers did not wholly follow or omit prescribed resources. Instead, they compared the prescribed resources with open online resources and other written material to supplement or modify the resources already planned. During implementation, they constantly formatively evaluated the effectiveness of the selected resources. The main influences on teachers’ decisions to follow, adapt, or omit resources were teachers’ experience and beliefs, students’ needs and perceived cognitive abilities, systemic influences, and teachers’ intentions to enhance students’ affective needs (such as motivation, engagement, and perceived relevance). The study sheds light on the complex process of planning, implementing, and evaluating the effectiveness of teaching resources moment-by-moment. It also underscores the need for teacher educators to equip pre-service teachers with skills to effectively observe students’ behaviors, interpret students’ work, and develop effective questioning techniques to explore students’ understanding. The study highlights the importance of reflective practice, professional development, and collaboration with colleagues to develop curriculum expertise continuously. Additionally, the study contributes to expanding Schoenfeld’s (2011) theoretical decision-making model, extending it to secondary mathematics teachers, and informing professional development efforts to support teachers in making informed and effective choices regarding the selection of curriculum materials and instruction strategies
INVESTIGATING UNDERGRADUATES’ LEARNING OF READING STRATEGIES TO COMPREHEND MATHEMATICAL PROOFS
Get PDFIn this dissertation, I report results from a study that investigated the impact of students’ engagement in a series of tasks in an introductory proof course that was designed to stimulate their learning of reading strategies to support their comprehension of mathematics proofs. Specifically, I investigated the impact of the design of five self-explanation tasks, designed through principles of variation, on undergraduates’ discernment of reading strategies; and if students’ learning of specific reading strategies influenced their comprehension of the proofs they read. The goal of this study was to answer two questions: How do undergraduate students in an introductory proof course who engage in self-explanation training tasks, designed and implemented using principles from Variation Theory, develop the capacity to use effective reading comprehension strategies to read proof? How does using Variation Theory as a design principle in self-explaining tasks support undergraduates’ learning of proof reading strategies and their proof comprehension? The study reports on data collected from 8 undergraduate students enrolled in an introductory proof course across a 15-week semester. I conducted this study to investigate and model students’ learning and development of four strategies for reading mathematics proofs across a semester, which used qualitative methods employing six main data-collection methods. The six qualitative methods I used included administering a pre-post comprehension assessment, administering a demographic survey, conducting participant observations, conducting a verbal think-aloud protocol (Cho, 2020) and semi-structured interviews; and collecting written work from students. I then used deductive coding approaches (i.e., a priori coding) to analyze students’ responses to assessments, inductive coding approaches (i.e., open, axial, and selective coding) to analyze student responses to self-explanation task assignments, and a combination of both coding approaches for data collected about students’ engagement in verbal think-aloud protocols, semi-structed interviews, and field observations. However, students responses to the demographic survey was used to introduce participants in each of their cases and to contextualize findings obtained in other data sets. In response to the first research question, the findings of this study suggest that undergraduate students in the chosen introductory proof course who engaged with the self-explanation tasks, designed and implemented using principles of Variation Theory developed an understanding of most characteristics and features associated to the four chosen reading strategies. Though students developed an understanding of features and characteristics associated to each of the four reading strategies that were learning objectives of the study, they did not use the reading strategies in their reading of subsequent proofs in the study. Research on the use of Variation Theory (see Kullberg et al., 2017) have argued that well-designed tasks are not sufficient for learning to occur because students should also engage in instructional environments that promote their discernment of features. However, findings from this study suggest that students’ were immersed in an instructional environment intended to be entirely student-centered, but the instruction was enacted in an instructor-centered way, which was opposite to the active involvement of students in their own learning promoted by the designed tasks. In students’ instructional environment, their understanding of the reading strategies also did not transfer into them using the strategies since they also heavily read their proofs verbatim during their class presentations, despite being instructed to do otherwise. However, findings from the pre and post assessments also suggest that students experienced an overall positive change in their reading comprehension after engaging with the tasks (i.e., the start of the semester to the end of the semester). Most of the positive change that occurred in students’ reading comprehension was in their holistic comprehension. Specifically, those students experienced an increase in their ability to understand a proven statement, comprehend the purpose of a sentence within a proof framework, identifying a good summary for a proof, identifying the structure of a proof, and transferring the general ideas or methods to another context. Another purpose of this study was to investigate how using Variation Theory as a design principle in self-explanation tasks would support undergraduate students’ learning of reading strategies to comprehend mathematics proofs. In response to my second question, the findings of this study suggest that using Variation Theory as a design principle for the design and implementation of tasks were effective at creating learning opportunities to promote students’ discernment of the intended variation in each task. Specifically, findings suggest that these learning opportunities promoted students’ discernment of distinguishing features associated to each reading strategy. However, the design of the tasks was insufficient to promote students’ use of the strategies in their reading of subsequent proofs. This study presents several implications for different stakeholders that either have direct or indirect affiliations associated to undergraduate introductory proof courses. Specifically, the findings of this study may be of relevance for instructors of introductory proof courses, mathematics departments, organizations dedicated to undergraduate program design, community of reading and literacy research, and the community of equity and social justice researchers. The implications presented in this study suggest integrating the designed tasks into introductory, advanced mathematics courses, design modifications that should be made to the study, and disparities that were brought to the fore related to some students’ diverse linguistic backgrounds. Future research should focus on replicating the study with larger sample sizes and investigating the effect of complementing the design of the tasks with instruction that calls attention to the variation present in each task
ENGINEERING BIOMATERIAL INTERFACES FOR MICROBIAL CONTROL
Get PDFSince its inception as early as ancient Chinese placing bamboo pegs in place of missing teeth over 4,000 years ago, biomaterials have been an indispensable component of medical tools at human’s disposal. While early implants rely solely on the material properties themselves, modern devices have become much more than just materials. Topographic features, coatings, surface energy, and even embedded electronics have all added dimensions to the complexity of biomaterials and medical devices. Interaction between these materials and host cells and tissues, as well as microbes that can cause infections. Although well recognized for its significance, controlling biomaterial associated infections is challenging due to high level tolerance of attached bacteria to conventional antibiotics. The purpose of this PhD study is to design and engineer biomaterials for better microbial control, e.g., improving antifouling behavior and antibiotic treatment efficacy. To better understand how biomaterials interact with the human immune system to clear infections, we developed an assay to screen suitable implant topography for bacteria clearance by host macrophages. This led to the discovery of critical recessive pattern dimensions that attenuate phagocytosis of bacterial cells. In addition, a prototype antifouling catheter with active topography was engineered for testing in a rabbit model of catheter-associated urinary tract infection. This design was inspired by the cilia on human endothelial lining and was shown to have antifouling capabilities in vitro against uropathogenic E. coli biofilm formation. In addition to topographic features on biomaterials, this study also explored low-cost embedded electronics for microbial detection. Specifically, a novel LC sensor system was developed to detect bacterial growth on surfaces, reporting the fastest phenotypical antibiotic susceptibility to date. It has potential to be integrated with implantable medical devices. These findings and engineered devices will help shape the next generation of rationally engineered implants that can sense and respond to microbial adhesion, and thus prevent and treat related infections
POPULATION DYNAMICS IN MYXOCOCCUS XANTHUS DEVELOPMENTAL BIOFILM
Get PDFMyxococcus xanthus, a soil-dwelling bacterium, exhibits complex multicellular behaviors through self-organization into biofilms. M. xanthus cells traverse agar surfaces, forming either predatory biofilm or vegetative swarm that expands outward in the presence of nutrients. Upon nutrient depletion, the swarm reorganizes as cells “stream” inward, coalescing into aggregates that mature into spore-filled fruiting bodies. This starvation-induced biofilm development is a complex process, governed by stringent genetic controls and coordinated population interactions. Despite extensive research into the dynamics of this development, from the onset of starvation to fruiting body maturation, a comprehensive understanding is still missing. This dissertation sheds light on the population dynamics during the early and late stages of M. xanthus starvation-induced biofilm formation. In this study, we demonstrate that streaming, a multicellular behavior, is not essential for the initiation of nascent aggregates. By integrating four key features—cell movement, local alignment, local density, and stream persistence—we developed a stream detection mask applicable to various M. xanthus strains. The stream mask can pinpoint the location of streams, both in time and space. Our findings reveal that where an aggregate initiate does not depend on streams, which are randomly distributed rather than being concentrated around aggregates with higher probability. Furthermore, by examining strains deficient in either of the two motility systems, we established that streaming and aggregation are independent phenotypes. A mutant lacking adventurous motility formed aggregates without streaming, indicating a potential link between adventurous motility and streaming. The mutant deficient in streaming aggregated more slowly than the wild type, suggesting that streams might enhance aggregation efficiency by facilitating faster aggregation. Additionally, we investigated the population dynamics influencing sporulation phenotypes by varying aliquot volumes, comparing cell distribution of aliquots of equal volume placed in one large spot versus multiple smaller spots, and adjusting the proximity of cell spots in sporulation assays. We identified these parameters as optimizable for enhancing sporulation efficiency and reproducibility. Large aliquot volumes correlated with reduced spore recovery, likely due to a higher number of elongated aggregates. Distributing an equal number of cells into five smaller spots, compared to one large spot, resulted in a twofold increase in spore recovery. Testing spot proximity revealed a novel 1-3-5 effect, where spore recovery decreased with increasing spot distance up to 3.5 cm before increasing again. This phenomenon was observed among mutant strains as well and it required cells of the same genotype to be on the same agar surface. We hypothesize that a diffusible signal might be involved. Thus, in this thesis we provide significant insights into M. xanthus development, investigating the role of streaming in nascent aggregation and introducing new factors influencing sporulation efficiency. These findings enhance our understanding of M. xanthus development and offer valuable knowledge and tool applicable to various bacteria and amoebae capable of forming developmental biofilms
EFFECTS OF NEGATIVE POISSON’S RATIO ON THE MECHANICS OF AUXETIC CARBON FIBER COMPOSITES UNDER TENSILE, BUCKLING AND LOW VELOCITY IMPACT
Get PDFCarbon fiber reinforced polymer (CFRP) matrix composites exhibited superior properties, such as high specific stiffness and specific strength, excellent fatigue and corrosion resistance, and low coefficient of thermal expansion, have been popular across various industries including aerospace, marine, automotive, energy, civil infrastructure, and high-end sports over the past decades. However, one significant drawback of CFRP composites is the susceptibility to low velocity impact damage which, for aircraft, can be results of tool drop, runway debris, and bird strike during takeoff and landing. These impact events could lead to external and internal damages of a CFRP composite structure in various damage modes, such as fiber breakage, delamination, matrix cracking, which will significantly compromise the structural integrity. Introducing auxeticity or negative Poisson’s ratio is one potential solution to mitigate the low velocity impact damage of CFRP composites, which can be achieved by tailoring the layup of an anisotropic composite laminate. Such special layups involve use of nontraditional ply orientations other than the quad layups with ply orientations of 0°, 90°, +45°, -45°, and the effects of such layups on the other apparent mechanical properties are yet to be investigated. This work aims to investigates the impact of introducing in-plane or out-of-plane auxeticity (negative Poisson’s ratio) in carbon fiber reinforced polymer (CFRP) composite laminates to examine their mechanical performance, particularly under tensile, uni-axial bucking and low velocity impact through both experimental tests and numerical simulations. In this work, the in-plane auxetic and counterpart non-auxetic laminates have a layup of [15/65/15/65/15] and [35/60/-5/60/35]. For out-of-plane auxetic and non-auxetic laminates, the layups are [25/-25/25/-25/25] and [50/0/50/0/50], respectively. Tensile tests on laminates with various in-plane and out-of-plane Poisson’s ratios revealed that auxetic layups could significantly alter ultimate tensile strength. Laminates with in-plane negative Poisson’s ratios demonstrated considerably lower tensile strength (51.7% on average) than their Positive Poisson’s ratio counterparts, whereas out-of-plane auxetic laminates showed moderately lowered (23.1% on average) tensile strength than the counterpart non-auxetic laminates. Strain field analysis, supported by digital image correlation and finite element simulations, highlighted stress concentrations near specimen gage sections, influenced by the unbalanced layup designs. Auxetic laminates were found to have a more imminent first ply failure as well as ultimate tensile failure due to transverse strain aggregation. Experimental findings also reveal that auxetic laminates can triple the buckling strength under uniaxial compression compared to non-auxetic counterparts, attributed to the unique effects of negative Poisson’s ratios. A novel monoclinic plate-based approach was used to isolate the influence of auxeticity from changes in the bending stiffness matrix, confirming that auxeticity actively contributes to enhanced buckling strength, though this effect is sensitive to stiffness matrix elements, as well as the loading conditions and plate aspect ratios. Numerical simulations and experimental tests demonstrate that auxetic laminates experience significantly reduced delamination, matrix compressive damage, and fiber tensile damage under low velocity impacts at higher impact energies. The results underscore the potential of auxetic designs to improve the impact resistance and buckling stability of composite laminates but also highlight the need for careful consideration of other mechanical properties, such as tensile, compressive, and bending strengths. The findings provide critical insights for designing advanced composite structures with enhanced performance, leveraging the benefits of negative Poisson’s ratios while managing trade-offs in other structural properties
COGNITIVE LOAD CLASSIFICATION FROM FUNCTIONAL NEAR-INFRARED SPECTROSCOPY DATA
Get PDFPredicting cognitive workload using physiological sensors, such as functional near-infrared spectroscopy (fNIRS), has gained significant attention in recent years. However, many existing methods are limited by small datasets and narrow brain channel coverage, restricting their generalizability across participants, tasks, and sessions. In this thesis, we introduce two innovative approaches aimed at overcoming these limitations: a CNN-BiGRU model with self-supervised label augmentation (SLA) and a block-wise domain adaptation method (BWise-DA). Our CNN-BiGRU-SLA model, grounded in cognitive load theory, leverages attention mechanisms and multi-label classification to predict working memory load (WML) and visual processing load (VPL) across multiple participants and sessions. Using leave-one-participant-out (LOOCV) validation, we achieved F1-scores of 91.79% and 89.07% for binary classification of WML and VPL, respectively, and 79.72% and 79.68% for multi-level classification. The largest barrier to the application of fNIRS data is the high variance, which can arise between subjects and across sessions. In this thesis, we highlight that such variance can also occur within different blocks of the same session for the same subject. To address this, we introduce the BWise-DA approach, which effectively handles intra-subject and inter-subject variability by treating different blocks within the same session as distinct domains. This method minimizes intra-class domain discrepancy while maximizing inter-class domain distinction, enhancing the model’s ability to generalize. Additionally, we propose an MLPMixer-based model to further refine workload prediction. Experimental evaluations on three publicly available datasets—two involving n-back tasks and one involving finger tapping—demonstrate that our methods outperform baseline models. Furthermore, a visualization study shows that the models accurately focus on brain regions associated with the relevant tasks, confirming the model’s interpretability. These contributions establish a strong foundation for fNIRS-based workload prediction, paving the way for more accurate and generalizable models suitable for real-world applications